TANYA'S

COMPREHENSIVE GUIDE TO

FELINE CHRONIC KIDNEY DISEASE

 

 

ALL ABOUT HYPERTENSION (HIGH BLOOD PRESSURE)

 

ON THIS PAGE:


What is Hypertension


Why Monitoring Blood Pressure is So Important


How Common is Hypertension


Symptoms


Diagnosis


Important Numbers


When to Start Treatment


Blood Pressure Target


Treatments, Including Amlodipine, ACE Inhibitors (benazepril) and Telmisartan


All about Amlodipine


Hypertension Research: My Cat Can Help Study


 

 

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Renomegaly (Enlarged Kidneys)


Which Tests to Have and Frequency of Testing


Factors that Affect Test Results


Normal Ranges


International and US Measuring Systems


 

TREATMENTS


Which Treatments are Essential


Fluid and Urinary Issues (Fluid Retention, Infections, Incontinence, Proteinuria)


Waste Product Regulation (Mouth Ulcers, GI Bleeding, Antioxidants, Adsorbents, Azodyl, Astro's CRF Oil)


Phosphorus, Calcium and Secondary Hyperparathyroidism (Calcitriol)


Miscellaneous Treatments: Stem Cell Transplants, ACE Inhibitors - Fortekor, Steroids, Kidney Transplants)


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ESAs (Aranesp, Epogen etc.) for Severe Anaemia


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Home > Key Issues > Hypertension

 


Overview


  • Hypertension (high blood pressure) is very common in CKD cats, and can have some very serious consequences, including a stroke or blindness.

  • It may also damage the kidneys.

  • Therefore if at all possible, you must ensure your cat's blood pressure is checked regularly.

  • Hypertension can usually be easily controlled using medication.

  • The best medication is amlodipine (common trade names are Norvasc or Istin). It is effective, is unlikely to make blood pressure fall too low, and in some cases may even reverse blindness caused by hypertension.


What is Hypertension?                                                                                           


 

Hypertension means the pressure (or tension) in the arteries is elevated. This creates more work for the heart, and can eventually lead to damage to blood vessels.

 

Long Beach Animal Hospital has a section on hypertension in cats.

Newman Veterinary also discusses hypertension in cats.

Mar Vista Vet has an overview of high blood pressure in cats.

The American Veterinary Medical Association has an audio presentation about hypertension in cats which lasts about five minutes.

 

Types of Blood Pressure


One of the kidneys' functions is to help to control blood pressure. There are two kinds of blood pressure in cats:

  • systemic blood pressure i.e. within the cat's body generally; and

  • intraglomerular blood pressure i.e. within the kidneys in particular

It is not practicable to measure intraglomerular blood pressure in cats, so this page focuses on treatments for systemic hypertension, i.e. elevated blood pressure within the cat's body generally. There is more information on intraglomerular blood pressure here.

 

Primary and Secondary Hypertension


For many years it was thought that hypertension in cats was the result of another condition, such as CKD - this is known as secondary hypertension. According to Cornell University College of Veterinary Medicine, other conditions that may cause hypertension include hyperthyroidism, diabetes and heart disease.

 

Whilst it is true that hypertension is more common in cats with these conditions, it is gradually becoming clear that primary hypertension does exist in cats, and may in fact contribute to the development of CKD. If the blood vessels within the kidneys are damaged because of hypertension, eventually CKD can result. The National Kidney & Urologic Diseases Information Clearing House explains more about this.

 

Feline hypertension: risks and management (2005) C Atkins Presentation to the World Small Animal Veterinary Association Thirtieth World Congress says "adding to the confusion in understanding the pathogenesis of hypertensive renal disease, renal disease begets hypertension and hypertension begets renal disease."

 


Why Monitoring Blood Pressure is So Important                                           


 

Untreated hypertension can cause permanent damage to the heart, eyes, brain and kidneys (with the latter making the CKD progress faster), so it is very important to treat hypertension if it is present.

 

Unfortunately hypertension is not usually visible (there can be certain symptoms as described below, but most laypeople would not realise these can be warning signs of hypertension, and these symptoms are not always present). To obtain an accurate diagnosis, blood pressure needs to be measured, but unfortunately many vets do not routinely check CKD cats for hypertension, even though CKD patients are at increased risk of hypertension.

 


How Common is Hypertension?                                                                         


 

Prevalence of systolic hypertension in  cats with chronic renal failure at initial evaluation (2002) Syme HM, Barber PJ, Markwell PJ & Elliott J, Journal of the American Veterinary Medical Association 220 pp1799-804), found an incidence rate of high blood pressure of only 20% in cats at initial diagnosis of CKD. However, since the risk of high blood pressure developing increases as the CKD worsens, it appears that at least one third of CKD cats have high blood pressure. In fact, as mentioned in Changes in systolic blood pressure over time in healthy cats and cats with chronic kidney disease(2015) Bijsmans ES, Jepson RE, Chang YM, Syme HM, Elliott J Journal of Veterinary Internal Medicine 29(3) pp855-6, other studies indicate that the incidence of high blood pressure in CKD cats is as high as 65%.

 

The Bijsmans study found that increasing age is a significant factor in developing hypertension, but healthy cats were less at risk. Elevated kidney values were an independent risk factor for the development of hypertension. Therefore if you have a CKD cat, you should monitor blood pressure whatever the cat's age. It is also wise to monitor blood pressure in all older cats (over the age of nine.

 

Cats with hyperthyroidism are also prone to developing hypertension (87% in one study were found to have hypertension), so you need to be particularly careful if your cat has both hyperthyroidism and CKD. Using corticosteroids may also lead to hypertension.

 


Symptoms of Hypertension                                                                                                       


 

There are a surprising number of possible symptoms of hypertension in cats.


Urgent Symptoms of Hypertension


These symptoms, or target organ damage (TOD) as they are referred to in the ACVIM Consensus Statement: guidelines for the identification, evaluation, and management of systemic hypertension in dogs and cats (2007) Brown S, Atkins C, Bagley R, Carr A, Cowgill L, Davidson M, Egner B, Elliott J, Henik R, Labato M, Littman M, Polzin D, Ross L, Snyder P, and Stepien R Journal of Veterinary Internal Medicine 21 pp542–558 (see table on page 546), are serious because they are potentially life-threatening or may permanently affect your cat's quality of life. There is more about target organ damage below.

 

Neurological Problems


Up to 46% of cats with hypertension have neurological problems. These are more common if blood pressure is very high, or if it has suddenly worsened.

 

Stroke


A cat with untreated or uncontrolled hypertension may have a stroke. A stroke means that the blood supply to part of the brain is cut off. Symptoms of stroke include inability to move (see below), weakness on one side of the body, the head tilting to one side, circling and blindness.

 

If your cat has a stroke because of high blood pressure, there is a chance of recovery if treatment is started quickly enough. See below for more on this.

 

Davies Veterinary Specialists have some information on strokes in cats and dogs.

 

Seizures


These may be a symptom of hypertension. Seizures may take a number of different forms. There may be the classic jerking and loss of consciousness, but being "spaced out" or mentally absent, may also be a type of seizure. Harpsie' s website has more information on what seizures may look like.

 

Seizures in CKD cats may also be caused by high potassium levels, calcium imbalances, high levels of toxins, or metabolic acidosis. The use of metoclopramide (Reglan) for stomach problems or Advantage for fleas may lower the seizure threshold. Other possible causes of seizures include epilepsy or a brain tumour, but the other causes mentioned above are far more likely in a CKD cat and should therefore be considered first.

 

Sometimes cats can appear blind after seizures and you will get a negative menace response, but this should not last for long, and in fact they are not normally blind - Harpsie had a negative menace response after his seizures and several vets were convinced he was blind, but he could still see well enough to play with Cat Dancer.

 

I am really surprised how many vets do not seem to realise that seizures may be caused by hypertension. I have lost count of the number of cats I've heard about who have simply been put on phenobarbital (an epilepsy medication) rather than having their blood pressure measured. In every single one of these cases, once the cat was given appropriate blood pressure medication, it was possible to stop the phenobarbital (which should always be done gradually) and the seizures never returned.

 

Having said that, occasionally cats who have had a stroke will start to have seizures, and in such cases anti-convulsant medication may be required.

 

Inability or Reluctance to Walk


If the hypertension causes a stroke, the cat may find it hard to walk, and may want to stay in one place, or may seem to have weakness in the legs.

 

Other causes of weakness in the legs include low potassium levels or high phosphorus levels leading to secondary hyperparathyroidism. Muscle wasting may also be caused by metabolic acidosis, while weakness in the back legs is occasionally caused by low magnesium or low calcium levels. General weakness may be caused by anaemia, or because the cat is simply not eating enough. If your cat is diabetic, back leg weakness may be caused by diabetic neuropathy.

 

Headaches and Head Pressing


Humans with high blood pressure often report having a very bad headache. There is no way to know if our cats have a headache, but I have heard of a  couple of cats pressing their heads against walls, which might be indicative of a headache. Such behaviour is sometimes also seen in cats with brain tumours.

 

Twitching


Twitching may be caused by high blood pressure. Other causes of twitching include high or low potassium levels, high blood pressure, high phosphorus levels, calcium imbalances (especially head twitching), hyperthyroidism or Vitamin B deficiency. Twitching may also be caused by high toxin levels. If your cat only twitches while you are giving fluids, it is probably caused by either the type of fluid used or by giving cold (room temperature) fluids.

 

Pharaoh's Shakes is a video showing a CKD cat twitching.

Pet MD mentions that twitching may be caused by kidney disease.

 

Ocular Problems


 

Blindness, Particularly Sudden Blindness (Retinal Detachment)


Unfortunately this is a relatively common occurrence in cats with untreated hypertension. The hypertension causes the retinas to detach, so the cat becomes blind.

 

You may notice a change in your cat's eyes, such as dilated pupils or uneven pupils (uneven pupils are known as anisocoria), or you can try moving your hand towards your cat's face and see if s/he reacts (a positive menace response) or not (a negative menace response). Another option is to get your cat's attention, then drop a cotton wool ball and see if the cat follows the ball with his/her eyes.

 

Blindness may also manifest itself in a less obvious manner. e.g. your cat may no longer jump and climb, which you might ascribe to weakness, when in fact it is caused by an inability to see where s/he is jumping. Your cat may also walk differently, perhaps keeping to the side of rooms, or walking through food (because s/he cannot see it).

 

Even if your cat's retinas detach because of high blood pressure, if treatment is started quickly enough, there is a chance of the retinas re-attaching and your cat regaining some sight. See below for more on this.

 

One other possible cause of blindness in cats is the use of an antibiotic called Baytril, though this is extremely rare if dosage guidelines are adhered to.

 

Sometimes cats can appear blind after seizures and you will get a negative menace response, but this should not last for long, and in fact they are not normally blind - Harpsie had a negative menace response after his seizures and several vets were convinced he was blind, but he could still see and play with Cat Dancer.

 

Hypertension in cats and dogs (2002) Stepien RL Presentation to the Waltham/OSU Symposium: Small Animal Cardiology 2002 has a photo of a cat with detached retinas.

Pet Place has an article about detached retinas, including information on other possible causes (no need to register to read this, just click Close at the bottom of the annoying pop-up window).

Feline hypertensive retinopathy (2007) is an article by Christi Benigni of Washington State University.

VCA Hospitals have some information on anisocoria (uneven pupils).

 

Bleeding Eyes (Retinal Haemorrhage)


These may also be a sign of hypertension. The bleeding happens in the front chamber of the eye, so it is visible. This type of bleeding is known as hyphema. Cats with retinal haemorrhage are not usually blind.

 

Long Beach Animal Hospital has a photograph of a cat with a bleeding eye.

International Cat Care has a photograph of a cat with this problem.

Pet Place has some information about hyphema.

 

Heart Problems


Hypertension can damage the heart because the increased blood pressure places a strain on the heart, which has to pump blood around the body. The most common finding is left ventricular hypertrophy, which means the left ventricular chamber of the heart is enlarged. Obviously you would not be able to see this, but here are some possible heart-related signs of hypertension.

 

Nosebleeds (Epistaxis)


Although nosebleeds in themselves may not appear too serious, in a cat with hypertension they may be a sign of heart damage caused by the hypertension.

 

Dental abscesses or a low blood platelet count may also cause nosebleeds.

 

Pet Place has some information about nosebleeds (no need to register to read this, just click Close at the bottom of the annoying pop-up window).

 

Heart Murmurs and Galloping Heart Rhythm


These are possible signs of heart problems caused by hypertension, though they may also indicate heart problems with other causes. In some cases a heart murmur is not a cause for concern, especially if it is not of recent origin (see Heart Problems), but Blood pressure in small animals Part 2: hypertension target organ damage heart and kidney (2009) Carr AP & Egner BE European Journal of Companion Animal Practice 19(1) pp1-5 states that "A new murmur or gallop rhythm should always lead to a blood pressure measurement."

 

Lethargy


Cats with heart problems caused by hypertension may be lethargic. You may also see lethargy in cats with neurological problems caused by hypertension.

 

Anaemia may also cause lethargy, as may high or low potassium levels, other types of heart problem and fluid retention.

 

When to Go to the Vet


I am often asked when to seek veterinary help for these symptoms. I know it can be expensive going to the ER or out of hours vet, especially if funds are tight. I personally would seek veterinary help as follows:

  • If you think your cat has had a stroke, I would go to the vet immediately. A stroke is a medical emergency, so if it is out of hours, I would still go to the vet as soon as possible, i.e. the ER or out of hours vet. The sooner treatment begins, the better the chances for survival, and without permanent disability. According to Veterinary Partner, starting treatment within six hours of the stroke "appears to be protective to neurologic tissues."

  • If you think your cat has gone blind, the sooner you start the medication, the more likely that s/he will regain the lost vision, so I would seek a same day appointment if the vet is open. I would be prepared to wait overnight but if it were any longer than that, perhaps because of a holiday weekend, I think I would go to the ER or out of hours vet. How quickly you notice the blindness is also a factor: if you realise very quickly, you have more room for manoeuvre than if it suddenly dawns on you and you realise that actually, your cat has probably been blind for several days or a week.

  • If you think your cat has heart problems caused by hypertension, I would check the Heart Diseases page to see if other urgent symptoms are present. If my cat appeared to have other urgent symptoms, I would go to the vet, ER or out of hours vet immediately. If my cat only had milder symptoms, such as nosebleeds, I would seek a same or next day appointment,  as long as my cat did not appear to be distress. If it was the weekend or a holiday, I would keep my cat quiet and get in to see my vet as soon as possible after they opened. Keep a close eye on your cat and be prepared to go to the ER or out of hours vet if your cat seems to be worsening.

  • if you think your cat has had a seizure caused by hypertension, or if you are seeing other possible signs of neurological problems caused by hypertension, I would seek a same or next day appointment, as long as my cat did not appear to be in distress (cats often seem fine after a seizure) and as long as there was only one seizure. If it was the weekend or a holiday, I think I would wait until my vet opened again, but if my cat had further seizures, I would probably be so frightened I would go to the ER or out of hours vet because I would worry myself silly otherwise. If you cannot afford to do that, it may well be safe to wait, but keep a close eye on your cat. If your cat starts to have one seizure after the other (which fortunately is unlikely), it is a medical emergency and you need to go to the vet, ER or out of hours vet as soon as possible.

Other Symptoms of Hypertension


 

Worsening Kidney Values


Since hypertension can adversely affect the kidneys, one possible symptom is a worsening of kidney values in bloodwork, particularly if it appears to occur quite suddenly. I recommend always having blood pressure checked in any cat whose bloodwork worsens unexpectedly.

 

Other Symptoms


These symptoms still indicate a need to test for and treat hypertension if it is present, but you do not need to rush to the vet or ER. On the other hand, I would not accept an appointment a week or two into the future either. If you see these symptoms, try to be seen within a maximum of three days, but ideally faster, of course.

Howling, Especially at Night


In some ways, this is the classic symptom of feline hypertension for me. I have lost count of the number of people who have told me their cat was doing this with no other likely cause as described below, I suggested the cat should be tested for hypertension, and the cat was indeed found to have hypertension.

 

Other possible causes include toxin levels, deafness, hyperthyroidism, or occasionally just old age and possibly cognitive dysfunction (senility).

 

Certain medications such as periactin (Cyproheptadine) or mirtazapine (Remeron), both appetite stimulants, or anabolic steroids can make a cat become vocal. Metoclopramide (Reglan), sometimes used for nausea and vomiting, may also have this effect.

 

Red and/or Hot Ears


A number of people have reported this symptom over the years. In all cases, the cat has turned out to have hypertension, often with a systolic reading over 200 mm Hg. Alternatively, red ears are sometimes seen in cats with food allergies.

 

Blood in Urine


This can be a sign of hypertension. It may also indicate the presence of a urinary tract infection, or kidney stones. There is a condition called "benign renal haematuria" which means there is bleeding from the kidney but the cause is not known; however, this is rare in cats.

 

Severe or ongoing haematuria may cause or worsen anaemia, so you should always take your cat to the vet if you see this symptom.

 

Persistent haematuria and proteinuria due to glomerular disease in related Abyssinian cats (2008) White JD, Norris JM, Bosward KL, Fleay R, Lauer C & Malik R Journal of Feline Medicine & Surgery 10(3) pp219-29 discusses how in Abyssinian cats with haematuria, the cause may be glomerular disease.

Long Beach Animal Hospital mentions (under Physical Exam) that blood in the urine may be a sign of hypertension.

Pet Place has some information about haematuria in cats (no need to register to read this, just click Close at the bottom of the annoying pop-up window).

The Pet Checkup is a product that checks for blood in urine, and which may also be used to check for other issues, such as diabetes.

 

Pacing or Restlessness


Sometimes cats with hypertension will pace up and down or just act restless generally. This may also be a sign of hyperthyroidism or of pain. Cats on certain medications, such as metoclopramide (Reglan), cyproheptadine (Periactin) or mirtazapine (Remeron or Zistin) may also exhibit these symptoms, especially if they have been given a high dose.

 


How to Diagnose Hypertension                                                                          


 

Hypertension is often known as the silent killer because it is not usually apparent and can be hard to detect until there is a crisis and the above symptoms appear. There are a few subtle signs you or your vet might be able to detect (see below) but there is no guarantee you will see these and even if you do, you won't know how severe the hypertension is.

 

The ideal preventative measure is for your vet to monitor your cat's blood pressure regularly with proper equipment. 

 

Unfortunately, not every vet has the equipment with which to check blood pressure. If your vet does not have the necessary equipment, encourage him or her to purchase it. An alternative is to call around other vets in your area - some are happy to do a one off blood pressure check for non-clients for US$25 or so. My vet charges about £16 to check blood pressure.

Blood Pressure Measuring Equipment


Most vets use what is called indirect blood measuring equipment, which is wrapped around the cat's tail or a paw, rather like the equipment used on a human's arm to measure blood pressure.

 

Some vets use oscillometric equipment but doppler ultrasound equipment seems to be more popular, perhaps because, as Evaluation of Doppler ultrasonic and oscillometric methods of indirect blood pressure measurement in cats (2004) Habermann, CE, Morgan JD, Kang CW & Brown SA International Journal of Applied Research in Veterinary Medicine 2(4) pp279-289 found, the doppler method is the more reliable method in conscious cats.

 

With a doppler monitor, only the systolic pressure is measured.

 

How to Measure Blood Pressure


 

Preparation


Cats can suffer from "white coat syndrome", where their blood pressure rises from the stress of the vet or hospital visit, so it is best to make sure your cat is as relaxed as possible before any tests are run:

  • you should always try to be present when blood pressure is taken.

  • blood pressure should be tested before any other testing or handling is done.

  • blood pressure should be measured in a quiet room. If possible, try to give your cat 5-10 minutes to get used to the room before the blood pressure is measured.

  • if your cat is prone to stress at the vet's, it can sometimes help to cover the cat's head with a towel or blanket. This would probably make humans more stressed, but it does help some cats: we used to do this for Harpsie whenever he had blood taken and it definitely made him calmer.

  • the person taking the measurements should be experienced at taking blood pressure in cats.

 

Measuring Blood Pressure


Blood pressure is often measured using the cat's tail, though my vet uses a front paw.

 

It is normal to take several readings and average them out in order to have an accurate reading. ACVIM Consensus Statement: guidelines for the identification, evaluation, and management of systemic hypertension in dogs and cats (2007) Brown S, Atkins C, Bagley R, Carr A, Cowgill L, Davidson M, Egner B, Elliott J, Henik R, Labato M, Littman M, Polzin D, Ross L, Snyder P, and Stepien R Journal of Veterinary Internal Medicine 21 pp542–558 recommends discarding the first measurement, then measuring blood pressure at least three more times, preferably 5-7 times, to produce readings which show less than 20% difference overall. The average of these readings is the cat's blood pressure measurement.

 

You will normally be told your cat has a blood pressure of x, with x being a number, e.g. 160. See below for information on what the readings mean.

 

Cats get high blood pressure too: monitor it is a video by Dr Andrew Sparkes which clearly demonstrates how to measure blood pressure in cats.

Purdue University College of Veterinary Medicine also has a video showing how to measure a cat's blood pressure.

Use of the doppler blood pressure monitor for the hypertensive feline patient (Norsworthy GD & Tilley LP) shows how to use a doppler monitor.

The Cat's Meow Veterinary Hospital explains very clearly how to measure blood pressure in cats.

 

Measuring Blood Pressure at Home


Some people with CKD cats have purchased doppler blood pressure monitoring equipment for home use, and been trained in its use by their vet. Since blood pressure monitors are quite expensive, this won't necessarily be cheaper than having checks performed at the vet's (perhaps in the long run, for people with multiple cats), but it is definitely more convenient, and it avoids the problem of "white coat syndrome", where a cat's blood pressure appears to be higher than it is because of the stress of being at the vet's. If possible, try to test the model you are thinking of purchasing before going ahead; I bought one but never really mastered using it (my cat was small and dainty, and even my vet struggled to measure her blood pressure).

 

Unfortunately the upfront cost of blood pressure monitoring equipment is too high for many people. In such cases, a possible compromise would be to find a vet or veterinary nurse/technician who is prepared to come to your home to measure your cat's blood pressure. This might cost more than taking your cat to the vet, but your cat will be less stressed and the blood pressure readings should be more accurate.

 

The following can be purchased for home use:

 

USA


Parks Medical (model no. 811) is a popular brand which has been used by a number of people dealing with CKD over the years. You do need a vet's prescription to buy one. It costs about US$620, essential accessories (cuffs etc.) cost extra, so your total cost will be in the region of US$1000.

 

Vmed Vet Dop Doppler is another brand which several people with CKD cats have purchased. With all the extras, it costs about US$1000.

 

Matrix Medical sells the Critikon Dynamap brand. The models for sale are refurbished and are therefore reasonably priced, though I must emphasise, I do not know anybody who has used one. If you mention you are a member of Tanya's Support Group, model number 8100 (item number 1582) complete with two cat-sized cuffs should cost US$200 and the XL (item number 1584) costs US$250 with two cat-sized cuffs. Shipping for either model costs approximately US$20.

 

UK


Thames Medical sells a CAT doppler blood pressure kit for £795.

 

Burtons Veterinary Products in the UK sells the 811 Parks model for £850. You may need to ask your vet to order it on your behalf.

 

Factors Affecting Blood Pressure Measurements


 

Effects of Stress on Blood Pressure Measurements


Some vets refuse to measure or treat blood pressure in stressed cats, claiming that the results will be inaccurate. Whilst stress may indeed affect the results, it will only do so by 20 or so points. In addition, according to Dr M Scherk in Blood pressure: a critical factor (2008), Presentation to the World Small Animal Veterinary Association World Congress, the usual method of measuring blood pressure in cats (doppler) tends to understate the result by around 14 points.

 

If you follow the tips above on how to measure blood pressure, you will minimise the risks of inaccurate results. If you see urgent symptoms as described above, such as a stroke or blindness, I would ask your vet to consider treating anyway. ACVIM Consensus Statement: guidelines for the identification, evaluation, and management of systemic hypertension in dogs and cats (2007) Brown S, Atkins C, Bagley R, Carr A, Cowgill L, Davidson M, Egner B, Elliott J, Henik R, Labato M, Littman M, Polzin D, Ross L, Snyder P, and Stepien R Journal of Veterinary Internal Medicine 21 pp542–558 says "The recommended approach to patient evaluation is based upon reliable measurements of blood pressure (BP). However, the identification and characterization of pre-existing target organ damage (TOD), the recognition of concurrent conditions (especially those causing secondary hypertension), and the categorization of risk for further TOD form the basis for treatment decisions."

 

"Spiking" Blood Pressure


It is normal for a cat's blood pressure to vary throughout the day. Diurnal variations of blood pressure in cats (2006) Mishina M, Watanabe N, Watanabe T Journal of Veterinary Medical Science 68(3) pp243-8  found that blood pressure in healthy cats peaked at 8 a.m. and 7 p.m..

 

Unfortunately sometimes a cat's blood pressure will "spike" (increase dramatically, then reduce to normal levels) at intervals, which means you may notice symptoms of hypertension in your cat but tests at the vet appear normal.

 

More worryingly, you may see no symptoms but your cat's blood pressure could be spiking and causing harm without you realising it.

 

I feel quite strongly about this because I lost one of my cats to the effects of spiking blood pressure. She did not have CKD, indeed her only health problem was hypertension. She therefore had been on amlodipine for several years and her blood pressure was always fine during vet checks (which were usually performed every 3-6 months), but she suddenly collapsed (briefly) at home one evening and a veterinary cardiologist discovered the next day that her heart had been damaged by hypertension. He was hopeful that bringing her blood pressure under proper control would improve her heart function and added another medication to her regimen for this purpose, but she collapsed and died at the vet's during a check up ten days later.

 

If you suspect your CKD cat may have spiking blood pressure, I would discuss with your vet how to test for this. One possible method would be for your cat to be kept at the hospital and to have blood pressure checked every hour. A better solution would be if you could borrow (or buy) a blood pressure monitor and check your cat's blood pressure frequently at home yourself after being shown how to do this.

 

Frequency of Blood Pressure Testing


The following suggestions are based on the ACVIM Consensus Statement: guidelines for the identification, evaluation, and management of systemic hypertension in dogs and cats (2007) Brown S, Atkins C, Bagley R, Carr A, Cowgill L, Davidson M, Egner B, Elliott J, Henik R, Labato M, Littman M, Polzin D, Ross L, Snyder P, and Stepien R Journal of Veterinary Internal Medicine 21 pp542–558. See below for blood pressure targets and treatment options.

 

For CKD cats without hypertension:

  • Test blood pressure at time of diagnosis of the CKD. Check it again 2-4 weeks later. If your cat does not have elevated blood pressure or signs of any problems, it should then be in order to test blood pressure every quarter.

For CKD cats with hypertension: 

  • The initial diagnosis should not be made based on measurements taken on one occasion only.

  • If you are starting or changing medication, you should check blood pressure 7-10 days after starting. Once blood pressure has reduced to a safe level, you should check it again in 1-4 months.

  • For cats with ocular or neurological problems, you should check blood pressure 1-3 days after starting medication. For hospitalised cats, blood pressure should be checked daily.

  • If the blood pressure has reduced too far (below 120 mmHg), you should decrease the dose or frequency or change the medication you are using. You should then check blood pressure 7-10 days after starting, or earlier if you are concerned about your cat's health. Once the blood pressure has increased to a safe level, you should check blood pressure again in 1-4 months.

  • If blood pressure remains too high, you should increase the dose or frequency or change the medication you are using (you may need to add another medication). You should then check blood pressure 7-10 days after starting, or 1-3 days if the cat is exhibiting ocular or neurological problems. Once the blood pressure has reduced to a safe level, you should check it again in 1-4 months.

In all cases, if your vet recommends testing more frequently, then I would do so.

 

What to Do if Blood Pressure Measuring Equipment is Not Available


The following tests are no substitute for the proper measurement of blood pressure using dedicated equipment, but if you live in the middle of nowhere with no blood pressure testing equipment available, at the very least ask your vet to perform them. See below for what to do for cats with suspected but not proven hypertension.

 

Retinal Examination


Firstly, you and your vet should regularly examine the retina (a fundic exam) - often there are retinal changes caused by hypertension prior to retinal detachment occurring, though unfortunately these are not always visible, even to a vet.

 

An older cat's pupils may not dilate and contract the same as in a younger cat so you should try to ascertain how your cat's pupils respond to light i.e. what is normal for your cat. 

 

Permanently dilated or unevenly dilated eyes, or bleeding eyes, require urgent veterinary assistance.

 

What your vet sees during an eye exam on a cat is a video presentation by Dr Wendy Zimmerman.

Vet Girl explains how to do a fundic exam.

 

Femoral and/or Jugular Pulse


You can also try to become familiar with the way your cat's femoral pulse feels (this is the pulse in the femur, the thigh bone). If your cat has hypertension, the pulse will usually feel stronger than the norm for your cat. Your vet can teach you how to assess this.

 

You can also watch for jugular pulsing: slightly elevate your cat's chin and watch in the jugular area (in the neck) - you shouldn't see any pulsing.

 

Pet Education has instructions on how to take the femoral pulse.

 

Enlarged Aorta


The aorta is the large artery running from the heart. A chest x-ray may show that it is enlarged, and in Feline cardiology: back to the basics, Dr JM Bright states "This change is often noted as a normal aging change in cats; however, an enlarged aortic root may also indicate systemic hypertension."  This was what alerted my cardiologist to the fact that my cat's hypertension was actually not under control.

 


Blood Pressure: Important Numbers                                                            


  • Hypertension is usually considered to be present when systolic pressure is over 145 mmHg.

  • Treatment is usually started when systolic pressure is over 160 mmHg.

  • The goal is systolic blood pressure below 150 mmHg.

  • Systolic blood pressure should not fall below 120 mmHg.


When to Start Treatment                                                                                      


 

The recommendations differ depending upon whether your cat has target organ damage or not.

 

What is Target Organ Damage (TOD)?


What is meant by target organ damage? Cats are considered to have target organ damage if they:

  • are showing the severe symptoms of hypertension described above; and/or

  • have kidney bloodwork which has worsened; and/or

The chances of your cat developing target organ damage depend upon whether s/he has hypertension and if so, for how long s/he has had it; how severe it is; whether it has been treated; and whether your cat has any other conditions that increase the risk of hypertension, such as hyperthyroidism.

 

The chances of target organ damage occurring in the future increase once blood pressure is consistently over 160 mmHg: ocular (eye) problems have occurred with blood pressure as low as 168 mmHg. The risk of ocular and neurological problems (seizures, stroke etc.) is much higher once blood pressure is over 180 mmHg.

 

ACVIM Consensus Statement: guidelines for the identification, evaluation, and management of systemic hypertension in dogs and cats (2007) Brown S, Atkins C, Bagley R, Carr A, Cowgill L, Davidson M, Egner B, Elliott J, Henik R, Labato M, Littman M, Polzin D, Ross L, Snyder P, and Stepien R Journal of Veterinary Internal Medicine 21 pp542–558 categorises the risk of target organ damage (TOD) as follows:

 

Average Systolic Blood Pressure Measurement (mmHg)

Risk  of Damage to Organs

Treatment Plan

Under 150

Minimal

No treatment necessary

150-159

Mild

Treatment is not normally necessary. However, it may be appropriate to begin or increase blood pressure medications if ocular or neurological signs are present

160 - 179

Moderate

Begin or increase blood pressure medications

Over 180

Severe

Begin or increase blood pressure medications

 

Treatment for Cats With Target Organ Damage (TOD)


ACVIM Consensus Statement: guidelines for the identification, evaluation, and management of systemic hypertension in dogs and cats (2007) Brown S, Atkins C, Bagley R, Carr A, Cowgill L, Davidson M, Egner B, Elliott J, Henik R, Labato M, Littman M, Polzin D, Ross L, Snyder P, and Stepien R Journal of Veterinary Internal Medicine 21 pp542–558 states that treatment should be started or the dose increased in any cat with target organ damage. This also applies to cats whose blood pressure is below 160 mmHg (a level at which a cat does not usually need blood pressure medication) if there are signs of target organ damage.

 

The International Renal Interest Society (2013) states that, for cats exhibiting target organ damage, treatment should begin immediately without the need to prove persistent hypertension.

 

If your vet does not have the necessary equipment to check blood pressure, but strongly suspects that your cat has hypertension because of target organ damage, it is usually wise to try amlodipine and see if your cat improves. ACVIM Consensus Statement: guidelines for the identification, evaluation, and management of systemic hypertension in dogs and cats (2007) Brown S, Atkins C, Bagley R, Carr A, Cowgill L, Davidson M, Egner B, Elliott J, Henik R, Labato M, Littman M, Polzin D, Ross L, Snyder P, and Stepien R Journal of Veterinary Internal Medicine 21 pp542–558 says "The recommended approach to patient evaluation is based upon reliable measurements of blood pressure (BP). However, the identification and characterization of pre-existing target organ damage (TOD), the recognition of concurrent conditions (especially those causing secondary hypertension), and the categorization of risk for further TOD form the basis for treatment decisions." If your vet is nervous about treating for hypertension on this basis, Veterinary Partner mentions that amlodipine is a pretty safe drug and is unlikely to cause the opposite problem of hypotension (low blood pressure), even in a cat whose blood pressure is not overly elevated.

 

Treatment for Cats Without Target Organ Damage


ACVIM Consensus Statement: guidelines for the identification, evaluation, and management of systemic hypertension in dogs and cats (2007) Brown S, Atkins C, Bagley R, Carr A, Cowgill L, Davidson M, Egner B, Elliott J, Henik R, Labato M, Littman M, Polzin D, Ross L, Snyder P, and Stepien R Journal of Veterinary Internal Medicine 21 pp542–558 makes the following recommendations (see the table on page 548):

  • for cats with blood pressure between 150 mmHg and 159 mmHg, treatment is not normally necessary but blood pressure should be checked again after seven days. If blood pressure is no higher and there are still no signs of target organ damage, the kidney disease and any other conditions present (e.g. hyperthyroidism) should be managed, and blood pressure should be measured again in 1-3 months.

  • for cats with blood pressure between 160 mmHg and 179 mmHg but with no signs of target organ damage, you can either choose to treat for hypertension or check blood pressure again in one month.

  • for cats with blood pressure over 180 mmHg, medication should be used even if there is no sign of target organ damage. "Although the panel does not recommend that a patient with high BP but no TOD be treated as an emergency, it is prudent to institute therapy and re-evaluations rapidly in animals with severe risk for TOD."

The International Renal Interest Society (2013) states that for cats who are not showing signs of target organ damage, blood pressure should be treated only if it is "persistently" above 160 mm Hg. It recommends measuring blood pressure multiple times over a 1-2 month period for cats in the moderate risk category, and measuring it multiple times over a 1-2 week period for cats in the severe risk category.

 

I am not convinced this is entirely practical for most people. How many of us have the time and money to take our cats to the vet several times a week to check their blood pressure? Is it fair to stress our cats in this way? Personally, I have always treated my cats for hypertension if their blood pressure was over 160 mmHg on two separate occasions 1-2 weeks apart, even if they did not show any signs of hypertension. Be guided by your vet.

 

Blood Pressure Target


Diurnal variations of blood pressure in cats (2006) Mishina M, Watanabe N, Watanabe T Journal of Veterinary Medical Science 68(3) pp243-8  found that the average blood pressure over a 24 hour period in healthy cats was 118.4 mmHg (with a range of 107.4 - 129.4 mmHg).

 

You are unlikely to reach this level, but then your cat is no longer a healthy cat. For CKD cats, The International Renal Interest Society (2013) states that the goal is to reduce blood pressure to under 160 mmHg and to reduce the risk of target organ damage. ACVIM Consensus Statement: guidelines for the identification, evaluation, and management of systemic hypertension in dogs and cats (2007) Brown S, Atkins C, Bagley R, Carr A, Cowgill L, Davidson M, Egner B, Elliott J, Henik R, Labato M, Littman M, Polzin D, Ross L, Snyder P, and Stepien R Journal of Veterinary Internal Medicine 21 pp542–558 recommends a blood pressure level below 150 mmHg and above 120 mmHg. They add "A gradual, persistent reduction of BP is the therapeutic goal. Generally, acute and severe decreases in BP should be avoided."

 

You do not want blood pressure to fall below 120 mmHg. If it does, your vet will need to adjust the dosage.

 


Treatment of Hypertension


 

Hypertension is usually easily controlled, which should help your cat feel better. Since hypertension can damage the kidneys, getting it under control may also have the pleasant side effect in some cats of improving their kidney values. At the very least, according to ACVIM Consensus Statement: guidelines for the identification, evaluation, and management of systemic hypertension in dogs and cats (2007) Brown S, Atkins C, Bagley R, Carr A, Cowgill L, Davidson M, Egner B, Elliott J, Henik R, Labato M, Littman M, Polzin D, Ross L, Snyder P, and Stepien R Journal of Veterinary Internal Medicine 21 pp542–558, "Antihypertensive therapy may slow disease progression in animals with CKD."

Treating Other Contributory Conditions


If your cat has a condition that is contributing to the hypertension, such as hyperthyroidism, it is important to treat that condition. Doing so may even mean the hypertension resolves without the need for additional treatment.

 

Sodium Restriction


Your vet may ask you to restrict your cat's sodium intake. The International Renal Interest Society states on page 2 that there is no evidence this is helpful for cats, and that it should certainly not take the place of medication.

 

ACVIM Consensus Statement: guidelines for the identification, evaluation, and management of systemic hypertension in dogs and cats (2007) Brown S, Atkins C, Bagley R, Carr A, Cowgill L, Davidson M, Egner B, Elliott J, Henik R, Labato M, Littman M, Polzin D, Ross L, Snyder P, and Stepien R Journal of Veterinary Internal Medicine 21 pp542–558 go further and state "In fact, sodium restriction activates the renin-angiotensin-aldosterone axis, and may actually increase BP in certain settings." They state "the panel recommends avoiding high dietary sodium chloride intake in hypertensive animals but does not recommend that a specific effort be made solely to restrict dietary sodium chloride intake."

 

If you do decide to try to restrict sodium intake at your vet's request, you should do it gradually.

 

The food data tables provide information about the sodium content of many cat foods available in the USA and UK. Please see the Nutritional Requirements page for more information about sodium and whether to reduce your cat's intake.

 

Medications


There are several classes of heart medication used to control blood pressure in cats. You may be offered amlodipine (a calcium channel blocker), benazepril (an ACE inhibitor) or, very occasionally, telmisartan. Most experts agree that amlodipine is the drug of choice, but for severe hypertension, you may need to add another medication.


Amlodipine


Why Amlodipine is the Preferred Treatment


The preferred treatment is a drug called amlodipine, which is a heart medication in the calcium channel blocker family. You may be offered generic amlodipine or you may be given a branded version - I have used both with no problems. Brand names include Norvasc in the USA and Canada and Istin in Europe and Australasia.

 

Amlodipine is the best choice because:

  • it is reasonably priced.

  • it takes effect quickly (usually within a week).

  • most importantly, it may help cats who have suffered a stroke, and may reverse blindness in cats who have suffered retinal detachment caused by the hypertension.

Amlodipine and Strokes


A stroke is a medical emergency. According to Veterinary Partner, starting treatment with amlodipine within six hours of the stroke "appears to be protective to neurologic tissues."

 

Even if you do not manage to get help within six hours, you should still ensure your cat is treated as soon as possible because improvements may still be seen.

 

Your cat may be quite inactive after a stroke, so make sure s/he is kept hydrated and takes in food. You may have to carry your cat to the litter tray for a few days, or use puppy pads. Don't give up hope: Vet Info states that "on average, most feline patients recover and return to normal in two to three weeks after the stroke."

 

Seizures are a relatively common symptom of hypertension in cats (they may have other causes too). Occasionally cats who have had a stroke will start to have seizures, and in such cases anti-convulsant medication may be required.

 

Vet Info has tips on caring for a stroke patient.

 

Amlodipine and Blindness


If your cat is blind because of hypertension, there is an approximately 50:50 chance of the retinas re-attaching and your cat regaining some sight if treatment with amlodipine is started quickly enough (usually within three days of detachment). Strangely, I have never seen this major advantage of amlodipine mentioned in the veterinary literature, but Plumb's Veterinary Drug Handbook says "some vision may be restored in about 50% of cases of blindness secondary to hypertension." Cornell University College of Veterinary Medicine says "“We can treat a cat’s high blood pressure with a drug called amlodipine, which may allow a retina to reattach itself, and the cat can get some of its vision back."

 

Even if you do not start amlodipine immediately, there is still hope: I know of several CKD cat who went blind but regained their sight, even though treatment was not begun for some time, in a couple of cases not for 2-4 weeks. The longest I know of was a cat who showed some improvement (I saw the photos) even though treatment was not begun for twelve weeks.

 

If your cat is blind and you can see a veterinary ophthalmologist, s/he may be able to suggest other measures in addition to the use of amlodipine to increase the chances of the retinas re-attaching; but many people just use amlodipine with the help of their general vet and see an improvement in their cat's vision.

 

What have you got to lose by trying amlodipine? Your cat may well regain at least some vision, and even in s/he does not, s/he will be safe from the other risks of untreated hypertension.

 

If your cat's retinas do not re-attach, do not despair, cats cope far better with blindness than humans do, and I would not consider blindness in itself to be grounds for euthanasia.

 

Davies Veterinary Specialists have advice on how best to help your cat cope with blindness.

 

Amlodipine Dosage


The usual amlodipine dose for cats is 0.625 mg per day but some cats need double this dose (1.25mg). Blood pressure in small animals Part 2: hypertension target organ damage heart and kidney (2009) Carr AP & Egner BE states "The higher doses are usually needed in heavier cats." In Renal disease: Chronic kidney disease (2006) Dr D Polzin says "Amlodipine is prescribed at a dose of 0.625 mg for cats less than 4 kg, and 1.25 mg for cats greater than 4 kg." In some cases, even lighter cats may need higher doses if their hypertension does not respond to the lower dose. However, you should start at the lower dose. Be guided by your vet.

 

It can take up to a week for amlodipine to work, though you may see results more quickly. Your vet should check blood pressure 7-10 days after starting amlodipine, though personally I prefer to check it after a week. If blood pressure remains severely elevated, the dosage may be increased to 1.25mg per day. See Frequency of Blood Pressure Testing for more information on when and how to consider dosage changes. Any changes (especially reductions) in dosage should be made gradually, to give the cat's body time to get used to the lower dose.

 

How to Cut Amlodipine into Cat-Sized Doses


The usual dose is 0.625mg per day, but since the tablets dispensed are often 5mg, this means you need to break the tablet into eight, a tricky thing to do. One method of doing this is to use flat-edged tweezers:

  • Snap the pill in half with your fingers.

  • Take the half-pill and grip it firmly in the tweezers so that the edge of the tweezers are gripping the piece right in the middle. Then just grasp the other half of the piece with your other hand, and snap it off. 

  • Repeat step 2 until you have eight pieces.

This method also works for the 2.5mg tablets (which you would usually divide into four rather than eight).

 

Generic amlodipine is also available, but these pills tend to be even smaller than brand name Norvasc, so you may find that overall there is no advantage because you waste more of the lower priced pills.

 

Other Methods of Administration


 

UK and Europe


In the UK a cat-sized version of amlodipine (0.625mg), made by Summit Veterinary Pharmaceuticals Limited, is available. I used this for my own cats, with no problems. The downside is that this form of medication is far more expensive (more than twice the price of generic amlodipine). The upside is that you know your cat is getting the exact dose every day.

 

Randomized placebo-controlled clinical trial of a chewable formulation of amlodipine for the treatment of hypertension in client-owned cats (2015) Huhtinen M, Derré G, Renoldi HJ, Rinkinen M, Adler K, Aspegrén J, Zemirline C, Elliott J Journal of Veterinary Internal Medicine 10.1111/jvim.12589 (Epub) tested a chewable form of amlodipine (1.25mg strength) and found that it was effective, plus 73% of the cats in the study were prepared to eat it voluntarily. I suspect the product used in this study was Vivelin, which was approved in Ireland in March 2015 and which will presumably be introduced commercially in Europe shortly.

 

USA


In the USA it is possible to have medications compounded (made specially for your cat in cat-sized doses, sometimes in flavoured form) by a compounding pharmacy. Capsules or liquid suspensions (a liquid form of medication) are available, but if you opt for this, make sure you use a reliable compounding pharmacy. If you use a compounded amlodipine suspension, you should keep it in the fridge and discard it after 14 days. 

 

Thriving Pets sells 100 0.625mg tablets for US$60. If you enter the word "tanya" (without the ") in the promotional code box, you will receive a 10% discount on orders over US$100. Shipping is free for orders over US$100 after the discount.

 

Some people in the USA have amlodipine made into a transdermal medication, but I would not recommend this, because it is hard to know how much of the medication is being absorbed when it is given in this way. In fact, a couple of Tanya's Feline CRF Support Group members have found that the transdermal amlodipine they have used has not successfully controlled their cat's blood pressure, whereas the more usual commercially available form has. Since amlodipine is such an important medication, if at all possible, I would use the other forms.

 

Amlodipine: Possible Side Effects


The worst side effect of using amlodipine generally appears to be that some cats may become a bit lethargic when first starting it, but this should wear off as their bodies get used to the medication - most cats eventually seem brighter once their blood pressure is under control. However, if in addition to lethargy you see any of the symptoms linked to low blood pressure mentioned below, contact your vet.

 

Other possible side effects include constipation, upset stomach and, rarely, dental problems (gingivitis), low potassium levels, swelling of the limbs or an increased heart rate. You should contact your vet if you notice an increased heart rate.

 

Amlodipine should be used with caution in cats with liver disease.

 

The US National Library of Medicine has some information about possible side effects in humans.

 

Amlodipine and Hypotension (Low Blood Pressure)


Amlodipine appears to be a safe medication for the vast majority of cats, and does not seem to lower blood pressure too far, as may happen with some other types of blood pressure medication. Indeed, Blood pressure in small animals Part 2: hypertension target organ damage heart and kidney (2009) Carr AP & Egner BE states "Adverse side effects from a rapid drop in blood pressure (weakness, syncope, organ failure) are rarely reported."

 

Possible signs of low blood pressure include lethargy, fainting, drinking more, nausea, pale gums, and fast and shallow breathing. If you are at all concerned about any of the symptoms you see, contact your vet who can check to see if your cat's blood pressure has fallen too low (below 120 mmHg).

 

Amlodipine: Interactions with Other Medications


The European Medicines Agency says (clause 4.8 on page 9) that "Cerenia should not be used concomitantly with Ca-channel antagonists as maropitant has affinity to Ca-channels." The University of Zürich Institute for Veterinary Pharmacology and Toxicology also mentions this (in German). In principle this means that amlodipine should not be used with maropitant (Cerenia), a treatment used for nausea and vomiting. 'Concomitantly' has a rather vague medical meaning in that it means during the same time period, but in this context I don't know exactly what time period the EMA is referring to, i.e. do they mean at the same time or on the same day? Both of these medications tend to be given once daily, so they have a relatively long effect. Maybe giving them both on the same day but 12 hours apart (i.e. one in the morning and one in the evening) would probably be acceptable, but check with your vet or pharmacist.

 

If you are using cimetidine (Tagamet) to control stomach acid, it may increase the effects of amlodipine (thereby possibly reducing blood pressure too far), so it would probably be safer to use another histamine H2 antagonist such as ranitidine (Zantac 75) or famotidine (Pepcid AC) instead.

 

As reported by The US National Library of Medicine, products which contain glucosamine and chondroitin (used to treat arthritis), such as Cosequin, have been known to raise blood pressure temporarily in some human patients, so speak to your vet about whether to continue using such products if your cat has hypertension. It is possible that the sodium base of some of these products may be a factor, so try to obtain a product without a sodium base if possible.

 

One study, Feline hypertension: diagnosis and management (2002)  Elliott J, 27th World Small Animal Veterinary Association Congress 2002, indicates that treating hypertension with amlodipine sometimes reduces potassium levels, so you should ensure your cat's potassium levels are monitored and supplementation begun if necessary.

 

Plumb's Veterinary Drug Handbook mentions that cyproheptadine, an appetite stimulant commonly used in CKD cats, may also have calcium channel blocking effects and cause low blood pressure. In theory this means there is a risk that cyproheptadine in combination with amlodipine could reduce blood pressure too far. It is probably safer not to use these two drugs together, but in practice many people seem to use both medications without any problems. Be guided by your vet.

 

Veterinary Links Recommending Amlodipine


Some vets may recommend other treatments for hypertension. In the UK in particular, you may be offered benazepril (e.g. Fortekor) and told this is sufficient to control your cat's high blood pressure. Although benazepril may sometimes be necessary in addition to amlodipine (see below), it is rarely a good first choice. Here are some links to show to your vet if necessary.

 

In Chronic kidney disease (CKD) in dogs and cats - staging and management strategies (2015) A Presentation to the Virginia Veterinary Medical Association 2015 Virginia Veterinary Conference,  Dr D Chew says "Calcium channel blockers do not offer direct renoprotection, but do control systemic blood pressure much better than ACE-inhibitors."

 

How I treat hypertension (2012) Atkins CE Veterinary Focus 22(1) pp17-23 states "the literature and clinical experience leads one to conclude that amlodipine is the single best agent for managing feline systemic hypertension", although he does also mention that in some cases he uses it in conjunction with other medications (see below).

 

The International Renal Interest Society (2013) recommends using amlodipine in the first instance.

 

ACVIM Consensus Statement: guidelines for the identification, evaluation, and management of systemic hypertension in dogs and cats states "In cats, although the renin-angiotensin-aldosterone axis may play a role in the genesis or maintenance of systemic hypertension, CCB are often the first choice for antihypertensive therapy due to established efficacy."

 

Blood pressure in small animals Part 2: hypertension target organ damage heart and kidney (2009) Carr AP & Egner BE European Journal of Companion Animal Practice 19(1) pp1-5 says "Amlodipine has been the medication that has allowed successful management of hypertension in pets, especially cats."

 

In Chronic renal failure in the cat (2006) Sparkes AH Presentation to the World Small Animal Veterinary Association World Congress, Dr Sparkes states "in cats monotherapy with amlodipine (a calcium channel blocker) is generally regarded as the treatment of choice for systemic hypertension."

 

Hypertension in cats and dogs (2002) Stepien RL Presentation to the Waltham/OSU Symposium: Small Animal Cardiology 2002 mentions that amlodipine "is the current antihypertensive medication of choice for cats."

 

Treatment of systemic hypertension in cats with amlodipine besylate (1997) Henik RA, Snyder PS & Volk LM Journal of the American Animal Hospital Association 33 (3) pp226-234 indicates that amlodipine appears to be a safe and effective treatment for hypertension in cats.

 


ACE Inhibitors: Benazepril etc.            


Some vets prefer to use heart medications known as ACE inhibitors, which include benazepril (Fortekor/Lotensin) and enalapril (Enacard), to treat high blood pressure. Although ACE inhibitors can work well in dogs, they are not the best first choice for cats to control hypertension because:

  •  They are also less likely to control blood pressure consistently. Dr D Polzin states in Renal disease: Chronic kidney disease (2006) "ACEI have not been found to be consistently effective in lowering blood pressure in cats with CKD." Blood pressure in small animals Part 2: hypertension target organ damage heart and kidney (2009) Carr AP & Egner BE European Journal of Companion Animal Practice 19(1) pp1-5 states "Blood pressure reduction achieved with an ACEi is usually relatively minor. ACEi as sole agents resulted in initial control of hypertension in only 6 of 16 hypertensives, after 6 months only 2 of 16 were still controlled."

  • unlike amlodipine, they do not seem able to reverse blindness caused by hypertension;

  • they may cause increases in creatinine levels when first begun.

Using ACE Inhibitors in Addition to Amlodipine


However, for really severe cases of hypertension which do not respond to amlodipine alone, it may sometimes be necessary to give ACE inhibitors in addition to the amlodipine. I had to do this for my non-CKD cat with hypertension. ACVIM Consensus Statement: guidelines for the identification, evaluation, and management of systemic hypertension in dogs and cats says "Combination therapy may be especially useful in cats, in which there is some evidence for a beneficial effect of ACEI in CKD and for an established antihypertensive efficacy of CCB. This approach is being evaluated but is in need of further study."

 

Feline hypertension: clinical features and therapeutic strategies (2004) Bright JM Presentation to the World Small Animal Veterinary Association World Congress 2004 discusses using amlodipine in conjunction with ACE inhibitors such as benazepril or enalapril for cats who do not respond to amlodipine alone.

 

The International Renal Interest Society (2013) recommends using an ACE inhibitor in addition to amlodipine if amlodipine alone is not sufficient to control blood pressure, but warns "Take care not to introduce CCB/ACEI treatment to unstable dehydrated cats where GFR [a measure of kidney function] may drop precipitously if CCB/ACEI are introduced before the patient is adequately hydrated."

 

If you do add an ACE inhibitor to your cat's treatment plan, be sure to get blood values checked 7-10 days after starting the ACE inhibitor. Blood pressure in small animals Part 2: hypertension target organ damage heart and kidney (2009) Carr AP & Egner BE European Journal of Companion Animal Practice 19(1) pp1-5 states "When using ACEi, it is important to monitor for azotemia as this can occur secondary to the vasodilator effect."

 

Feline hypertension: diagnosis and management (2002)  Elliott J, Presentation to the 27th World Small Animal Veterinary Association Congress 2002 also discusses the use of ACE inhibitors in addition to amlodipine in cats who do not respond to amlodipine alone, and recommends checking bloodwork if ACE inhibitors are added, since these drugs may cause an increase in creatinine levels.

 

Using ACE Inhibitors for Hypertension for Other Reasons


Some vets may wish to use ACE inhibitors because they do not want to activate the renin-angiotensin-aldosterone system (RAAS), which may sometimes happen when using amlodipine. Plumb's Veterinary Drug Handbook states "There is concern that using amlodipine alone for treating hypertension in cats with renal disease may expose glomeruli to higher pressures secondary to efferent arteriolar constriction. This is caused by localized increases in RAAS axis activity thereby allowing progressive damage to glomeruli. It is postulated that using an ACE inhibitor with amlodipine may help prevent this occurrence." There is more information about the use of ACE inhibitors for CKD cats generally here and about the RAAS here.

 

In Chronic kidney disease (CKD) in dogs and cats - staging and management strategies (2015) A Presentation to the Virginia Veterinary Medical Association 2015 Virginia Veterinary Conference,  Dr D Chew says ""Balanced" antihypertensive protocols use BOTH ACE-inhibitors and calcium channel blockers to best control intraglomerular and systemic hypertension."

 


Telmisartan


You may possibly be offered another treatment called telmisartan (Micardis or Semintra). Like ACE inhibitors, this medication tends to be used more for its other effects, and was approved in Europe in 2012 for the treatment of proteinuria in CKD cats under the trade name of Semintra. There is more information on telmisartan here.

 


Hypertension Research: My Cat Can Help


I am occasionally contacted about an FDA-approved trial of a hypertension medication for cats on a website called My cat can help. The website does not share any meaningful information, such as the name of the medication being tested, nor does it have any contact details, so I was concerned that it might not be a legitimate trial. However, I have been contacted by a reputable source which has alleviated my concerns about the legitimacy of the trial, and I do know which medication is being trialled but am not at liberty to divulge this.

 

Since this is a double blind study, there is a 1 in 3 chance that your cat will receive a placebo for the first 28 days rather than the medication. I am not sure I would want to take this chance in a cat with hypertension. However, if your cat is confirmed to have hypertension at the initial exam, you are under no obligation to continue with this 28 day trial. If you do proceed to the initial 28 day trial and your cat is receiving the medication, you may continue on to the next stage of the trial which lasts five months, but are under no obligation to do so. During this stage your cat would receive the medication rather than a placebo.

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Links on this page last checked: 15 June 2015

   

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TREATING YOUR CAT WITHOUT VETERINARY ADVICE CAN BE EXTREMELY DANGEROUS.

 

I have tried very hard to ensure that the information provided in this website is accurate, but I am NOT a vet, just an ordinary person who has lived through CKD with three cats. This website is for educational purposes only, and is not intended to be used to diagnose or treat any cat. Before trying any of the treatments described herein, you MUST consult a qualified veterinarian and obtain professional advice on the correct regimen for your cat and his or her particular requirements; and you should only use any treatments described here with the full knowledge and approval of your vet. No responsibility can be accepted.

 

If your cat appears to be in pain or distress, do not waste time on the internet, contact your vet immediately.

 

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Copyright © Tanya's Feline CKD Website 2000-2012. All rights reserved.

 

This site was created using Microsoft software, and therefore it is best viewed in Internet Explorer. I know it doesn't always display too well in other browsers, but I'm not an IT expert so I'm afraid I don't know how to change that. I would love it to display perfectly everywhere, but my focus is on making the information available. When I get time, I'll try to improve how it displays in other browsers.

 

You may print out one copy of each section of this site for your own information and/or one copy to give to your vet, but this site may not otherwise be reproduced or reprinted, on the internet or elsewhere, without the permission of the site owner, who can be contacted via the Contact Me page.

 

This site is a labour of love on my part. Please do not steal from me by taking credit for my work.

If you wish to link to this site, please feel free to do so. Please make it clear that this is a link and not your own work. I would appreciate being informed of your link.