 |
TANYA'S
FELINE CHRONIC RENAL FAILURE INFORMATION CENTRE
ANAEMIA
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
Introduction
Anaemia is relatively common in CRF cats, so it is important to know about it and to be prepared to deal with it.
Anaemia is a condition in which not enough red blood cells exist in the body. Red blood cells transport oxygen round the body, so if a cat does not have enough, he/she will not be able to function properly and will feel very tired and weak; other symptoms are discussed below. Red blood cells are produced in the bone marrow and last for around 70-80 days in cats.
2. Why Does Anaemia Occur in CRF Cats?
Healthy kidneys produce a hormone called erythropoietin, which stimulates the bone marrow to make the blood cells. As the kidneys fail in CRF, they cannot produce enough erythropoietin, so the bone marrow is not stimulated, blood cells are not produced, and a particular type of anaemia called non-regenerative anaemia results. In addition, a uraemic toxin called parathyroid hormone, which is not processed properly by damaged kidneys, may also adversely affect the production of erythropoietin. And finally the lifespan of red blood cells in renal failure patients is approximately 50% that of healthy cats.
How Stuff Works has a simple article about how blood cells are made. Understanding anaemia is an excerpt from a book by Ed Uthman.
3. Major Symptoms and Risks of Anaemia
It is very important to treat anaemia because it can have some serious effects on the body:
Haemoglobin is the main oxygen-carrying protein of red blood cells. Because haemoglobin is less concentrated in anaemia, the heart rate increases in an attempt to push the reduced amount of haemoglobin around the body. This faster heart rate is called tachycardia. Occasionally anaemia may cause a heart murmur.
The heart tries to provide more blood, and thus oxygen, to the body's cells by increasing the pressure with which it pumps.
Because of the lack of haemoglobin, there is less oxygen in the body's tissues. The cat therefore breathes more often and more deeply, and may appear to be breathless.
This is also caused by the lack of oxygen in the tissues, which means the cells cannot work as effectively.
The heart can only compensate for the lack of haemoglobin to a certain extent. Eventually, if the problem remains untreated, blood will build up and fluid will leak into body tissues. This causes swelling known as oedema. If oedema occurs in the lungs, it is known as pulmonary oedema and if it is left untreated this can kill the cat.
The University of North Carolina has some information on the risks of anaemia in connection with heart failure in humans. Virginia-Maryland Regional College of Veterinary Medicine has examples of breath sounds, including the sound a cat with pulmonary oedema makes.
You may also see some milder symptoms such as pale eyelids, or eating litter - please see Index of Symptoms and Treatments and Symptoms for more information.
As you can see, anaemia is potentially very serious - but fortunately it is also treatable.
Before deciding on the best course of treatment, your vet must ensure that it really is non-regenerative anaemia caused by the CRF that you are dealing with. There are quite a few other causes of anaemia, including gastro-intestinal bleeding, particularly if the anaemia develops suddenly; most cats with anaemia caused by the CRF become anaemic gradually. A Vitamin B deficiency can also cause anaemia; whilst feeding onions to cats causes a specific type of anaemia called Heinz body anaemia, and it is possible that garlic (which belongs to the onion family) may also be a risk. In addition, cats with a hyperactive thyroid who are being treated with methimazole may sometimes develop anaemia.
Inflammation or infection may also cause anaemia. This may be because if a cat has an infection, the cat's body will sequester iron away (i.e. iron is stored rather than released into the bloodstream), because bacteria thrive on iron. Since iron is necessary for blood cell production, anaemia may result. Washington State University College of Veterinary Medicine mentions that pyelonephritis (a kidney infection) may cause non-regenerative anaemia in some cats, and this happens to my cat every time he gets a bout of pyelonephritis. Cats with Inflammatory Bowel Disease may also develop anaemia.
Your vet can run tests to ascertain what sort of anaemia your cat has and whether it is regenerative or non-regenerative; but remember, there is a small chance of causing, or more likely, worsening anaemia if too much blood is taken from your cat for blood tests, so bloodtests should not be run too often on CRF cats.
Feline anaemias: a diagnostic challenge is a paper on the various causes of anaemia presented to the World Small Animal Veterinary Association (WSAVA) 2002 Congress by Urs Giger. Basic approach to anaemia diagnosis (2005) is a paper on the various causes of anaemia presented to the World Small Animal Veterinary Association (WSAVA) 2005 Congress by Harold Tvedten. Murray State University has technical information on the diagnosis and classification of anaemia. Merck Veterinary Manual discusses anaemia in a quite technical but useful manner. Antech Diagnostics has an article entitled Canine Anaemia (which covers cats as well).
Packed Cell Volume (PCV) or Haematocrit (HCT) Your vet will determine whether your cat has anaemia through a bloodtest called Packed Cell Volume (PCV), or occasionally a bloodtest called Haematocrit (HCT) which is very similar to PCV (see What Do All Those Test Results Mean?). PCV measures the ratio of red blood cells to total blood volume. It does not distinguish old blood cells from new but it is a still a useful and accurate test for anaemia. The blood is spun in a centrifugal machine and your vet measures what is left. Only a small amount of blood is needed for this test and many vets have the necessary equipment in their offices so you can get a result in a few minutes.
Technically, a cat is anaemic if the PCV level is below 30% (or with some labs, 25%), but you may not start to see any differences in your cat's behaviour until the level is closer to 20%. Below 20% is generally considered to be severe anaemia, and it really must be treated as a matter of priority. Dehydration will make PCV look higher than it really is, so once the cat is rehydrated, PCV will often have fallen.
One person has been using a machine he purchased from Ebay to measure PCV at home in order to spare his cat the stress of vet visits and himself the cost of frequent tests. He found the machine he purchased was pretty accurate (varied by about 2% from vet readings). You can read more about this here. Personally, if I was dealing with severe anaemia (PCV below 20%), particularly if my cat was on Epogen, I would prefer regular vet visits in order to get accurate readings and to have my cat checked over by the vet.
Reticulocytes (Regenerative and Non-Regenerative Anaemia) The PCV test shows if your cat is anaemic, but it does not show whether the anaemia is regenerative or non-regenerative. Regenerative anaemia means that the cat's body may be able to correct the anaemia without any external help, whereas with non-regenerative anaemia, the cat is going to need some help in the form of some kind of treatment. Most (but not all) cats with CRF and anaemia are suffering from a type of non-regenerative anaemia caused by problems with erythropoietin production (see Why Does Anaemia Occur in CRF Cats?).
The only way to know for certain which type of anaemia you are dealing with is by testing for reticulocytes; but this cannot be done unless the anaemia is already severe.
Reticulocytes are immature red blood cells. Since anaemia means there is a lack of red blood cells, the body's usual response is to try to generate more red blood cells, so normally you would see reticulocytes if the anaemia is regenerative - this shows that the bone marrow is still making blood cells. However, in non-regenerative anaemia (as often seen in CRF), the lack of erythropoietin means the bone marrow is not able to make blood cells, or not enough of them to replace old ones, so there will be few or no reticulocytes present.
The reticulocyte test is unlikely to be reliable unless the anaemia is moderate to severe - anaemia needs to be fairly bad before a brisk regenerative response is considered necessary by the cat's body - so many vets do not test for reticulocytes unless the PCV is below 20%. If the reticulocyte count is still low or zero despite the PCV being below 20% for five days or longer(at which stage of anaemia, the bone marrow would normally be busy making new red blood cells if it could), this indicates non-regenerative anaemia.
Since there is no point in measuring reticulocytes until PCV is below 20%, and since anaemia in a CRF cat is likely to be of the non-regenerative kind caused by the failing kidneys, many vets simply assume that a CRF cat with anaemia is suffering from non-regenerative anaemia and treat accordingly. This may not be a major concern for cats with PCV over 20%, when the standard treatments can be used and you have some time on your side while you try to bring the anaemia under control. However, for a cat with a PCV below 20%, where the anaemia is a more urgent problem and you need to act quickly, you will probably be considering the use of rhEpo (which only works for non-regenerative anaemia); and in view of the risks associated with this treatment, you might wish to have the reticulocyte test done to be sure you really are dealing with non-regenerative anaemia. Having said that, my vet felt it was more important that we start treating Thomas as quickly as possible, so we began rhEpo immediately rather than wait several days or more for the results of a reticulocyte test.
Cornell University College of Veterinary Medicine provides more information on this complex subject: click on the word Feline on the left of the page for further information, including a table of reticulocyte counts. Antech Diagnostics have information on how they run this test. Idexx Laboratories have some information on reticulocytes.
Mean Corpuscular Volume or Mean Cell Volume (MCV) This is a measure of red blood cell size. If your cat has a low MCV, this may indicate a lack of iron (which can cause anaemia), or in some cases chronic liver disease. Cornell University College of Veterinary Medicine has more information about MCV.
If a cat cannot manufacture sufficient red blood cells, s/he will become anaemic. Unfortunately the lifespan of red blood cells in renal failure patients is approximately 50% that of healthy cats, so this is another reason why CRF cats become anaemic.
A low red blood cell count is usually indicative of anaemia.
If the RBC count is high, this may be indicative of dehydration.
There are various treatments for anaemia, and which one you should use depends upon how severe the anaemia is. Your vet can advise you which is the most appropriate treatment, though you need to be aware that not all vets have used rhEpo (see below) or know much about it.
Haemoglobin, which as mentioned earlier is the main oxygen-carrying protein of red blood cells, needs iron for its production. Iron deficiency appears to be relatively common in CRF cats, so, in some cases, an iron supplement is all a cat needs to control anaemia. Iron supplements can be given orally or a monthly injection can be given, though the injection is into muscle so it can be painful. Generally speaking, all CRF cats with mild to moderate anaemia (PCV or HCT below 30%) would probably benefit from an iron and vitamin B supplement.
All iron treatments may cause constipation or stomach upsets, so they should only be given if they are necessary. If a cat has an infection, the cat's body will sequester iron away (i.e. iron is stored rather than released into the bloodstream), because bacteria thrive on iron. This means the cat's body will be unable to use any iron you give, so it is better to get any infection under control before using iron.
Phosphorus binders should ideally be given separately from iron, because the binders may reduce the absorption of the iron. Drugstore has some information about this interaction.
Pet Education discusses iron requirements in cats. Pet-tinic, apparently now also known as Pet Tabs Iron Plus, is both an iron supplement (containing iron proteinate) and Vitamin B supplement (see correcting vitamin deficiencies), and is very popular on the CRF Information List. The usual dose for a 10lb (4.5kg) cat is 1 ml twice a day (which equates to 5.4mg of iron a day), but do check with your vet in case your cat needs a different dose. KV Vet Supply will ship Pet Tabs Iron Plus to the UK. Click on Pet under Complete Catalogue, then click on Vitamins and Nutrition, then click on Supplements for Cats, and finally click on Blood Support for Cats; or just search for Pet tinic. It costs US$6.85 for 4 oz (February 2007), but shipping to UK is relatively expensive, at around US$27 (land) or US$39 (air). This company will also ship to Canada. California Veterinary Supply sells something similar to Pet-tinic called NutriVed for $6.99 for 4 oz, which has the advantage of containing folic acid, which Pet-tinic lacks. It is also available from Healthy Pets at a cost of US$9.99 for 4 oz. Natural Pets also sell Nutrived for US$9.99 and will ship to the UK. Shipping via USPS Express Mail for one or two bottles costs around US29.
Fer-In-Sol is an infant iron supplement containing ferrous sulphate which may be suitable for some cats: the dosage for a 10lb (4.5kg) cat appears to be 0.1 ml (yes, 0.1ml, not 1ml) twice a day (which equates to 5mg of iron a day); but do check with your vet about dosage, since this is not a veterinary product. Please note this is only iron, so you may need to supplement B Vitamins separately.
UK We used an iron supplement from Boots the Chemist called Sytron, which contained 27.5mg of iron per 5ml. Your vet can suggest an alternative brand and give advice on dosage.
If you are in the UK, you may be offered a newish product called Kaminox. This is a combination of B vitamins, iron and potassium. Alfamedic provides a list of the ingredients. There is a similar product in the USA called Amino B & K, available from Emerson Ecologics. I would not recommend using such products unless your cat has low potassium levels, which not all CRF cats do; giving potassium when it is not needed can be very dangerous. Please also be aware that ACE inhibitors such as Fortekor may make potassium levels rise; so if your vet has prescribed Fortekor, as so many British vets do, it might be wiser to use a different type of iron without the potassium.
Vet UK sells Kaminox for £29.49 for 120ml, with free UK shipping. Caledonian Cat Clinic sells Kaminox for £30.55 for 120ml. Vetscriptions sells Kaminox for £30.99 for 120ml.
Spatone is an interesting possibility if you live in UK. This is a spa water which contains naturally occurring iron. The manufacturers claim that using iron in this way makes it more easily absorbed into the body. The manufacturers know of several dogs taking the product without problems, and one Feline CRF Information listmember is now using this product on her cat with her vet's approval.
Spatone is sold in sachets, and a box of 28 sachets costs £6.90, though discounts may be available for four boxes of 28 sachets or more. The product does taste of iron, so the manufacturers recommend giving the product in additional water. They suggest using 0.5-1.5 sachets per day in cats, which would be the equivalent of 100mg of ferrous sulphate.
Correcting Vitamin B Deficiencies A lack of certain B Vitamins, such as Vitamin B12 or Folic Acid (Vitamin B9), can cause non-regenerative anaemia. Your vet can prescribe a suitable supplement, or give your cat Vitamin B injections. Generally speaking, all CRF cats with mild to moderate anaemia (PCV or HCT below 30%) would probably benefit from an iron and vitamin B supplement.
Be careful about using multivitamin supplements because they may contain other vitamins such as A and D which are not usually suitable for CRF cats. I would also not recommend giving Vitamin B via additions to sub-Q fluid bags. Please see the Food Composition and Nutritional Requirements page for more information about vitamins.
Vitamin B12 may be particularly helpful. Vitamin B12 in the form of methylcobalamin (rather than the more commonly available cyanocobalamin) is the neurologically active form of Vitamin B12, and is used by the body to correct neurological problems. Apart from its role in preventing anaemia, it appears to help cats with diabetic neuropathy, and has also been found by Feline CRF Information list members to be very helpful for various CRF-related problems, including incontinence and constipation. A possible starting dose would be 500mcg (0.5mg) a day, though some people give twice as much. Be guided by your vet. Methylcobalamin is often sold in the form of fruit-flavoured lozenges which some people do use to pill their cats successfully, though plain methylcobalamin tablets are also available, though less easy to find.
PDR Health has some information about methylcobalamin (this is a human site). Vitacost sells 200 plain methylcobalamin 500mcg (0.5mg) capsules for US$11.99. I ordered these myself on a Sunday evening, and received them on the following Tuesday. Bayho sells 180 1000mcg (1mg) plain methylcobalamin tablets for US$26.81. Although the site states that it only sells to health professionals, they will normally sell to individuals if you tell them it is for veterinary use. Vitamin UK sells a number of different types of methylcobalamin, click on Search, then type in methylcobalamin. Methylcobalamin Resources has details of suppliers in USA, UK, and New Zealand, some of whom will ship worldwide. Please note this site is recommending methylcobalamin for cats with diabetes, and the doses given may be too high for a CRF cat; ask your vet.
B Vitamins are sensitive to heat and light so are best kept in a cool dark place. Some vets add Vitamin B to the sub-Q fluids bag, but this is not a good idea because it can make the fluids sting; it can compromise the sterility of the bag; and giving vitamins in this way is very expensive.
I would avoid using multi-vitamin products, particularly two products called Hi-Vites and Felovite II, as a source of B vitamins. These products tend to be too high in Vitamins A and D for a CRF cat, and Felovite II also contains phosphorus. Several cats on the CRF List have not done well on Hi-Vites in particular.
If you are in the UK, you may be offered a newish product called Kaminox. This is a combination of B vitamins, iron and potassium. Alfamedic provides a list of the ingredients. I would not recommend using Kaminox unless your cat has low potassium levels, which not all CRF cats do; giving potassium when it is not needed can be very dangerous. Please also be aware that ACE inhibitors such as Fortekor may make potassium levels rise; so if your vet has prescribed Fortekor, as so many British vets do, it might be wiser to use a different type of B Vitamin without the potassium.
Vet UK sells Kaminox for £29.49 for 120ml, with free UK shipping. Caledonian Cat Clinic sells Kaminox for £30.55 for 120ml. Vetscriptions sells Kaminox for £30.99 for 120ml.
Provet in the UK sells a Vitamin B supplement that is phosphorus-free, which costs £8.32 for 30 tablets. Pet-tinic, apparently now also known as Pet Tabs Iron Plus, is both an iron supplement and Vitamin B supplement. The usual dose for a 10lb (4.5kg) cat is 1 ml twice a day (which equates to 5.4mg of iron a day), but do check with your vet in case your cat needs a different dose. KV Vet Supply will ship Pet-tinic to the UK. Click on Pet under Complete Catalogue, then click on Vitamins and Nutrition, then click on Supplements for Cats, and finally click on Blood Support for Cats; or just search for Pet tinic. It costs US$6.85 for 4 oz, but shipping is relatively expensive. California Veterinary Supply sells something similar to Pet-tinic called NutriVed for $6.99 for 4 oz, which has the advantage of containing folic acid, which Pet-tinic lacks. It is also available from Healthy Pets at a cost of US$9.99 for 4 oz. Natural Pets also sell Nutrived for US$9.99 and will ship to the UK. Shipping via USPS Express Mail for one or two bottles costs around US29.
David Jacobson's Pages provide details on many Vitamin B supplements in the USA, which you may prefer to use instead of Pet-tinic if your cat does not need iron.
If anaemia is not too severe, anabolic steroids may help improve anaemia or at least slow down its progression. They may also be beneficial for CRF cats with muscle wasting and as an appetite stimulant. Your vet may prescribe anabolic steroids in the form of either tablets or injections. Commonly used anabolic steroids in Europe are Nandoral (Ethylestrenol in tablet form) or Laurabolin (injectible Nandrolone). Winstrol-V (stanazole) was popular in the US but unfortunately, it appears to have been unavailable since September 2004, which apparently is related to some type of FDA regulation. It may still be obtainable from some compounding pharmacies.
Steroids may damage the liver so your vet will need to monitor your cat's liver values.
There is more information about steroids on the Treatments page.
Another possible treatment for anaemia is erythropoietin, which is sold under the names of Epogen, Eprex or Procrit. This is quite a complex subject, so it has its own section below.
These are another possible treatment but again, this is quite a complex treatment so it is discussed in more detail below.
Erythropoietin is the hormone made by healthy kidneys which stimulates the bone marrow to produce red blood cells. Since CRF cats can gradually lose the ability to make erythropoeitin, a synthetic version of human erythropoeitin known as Epoetin Alfa Recombinant or rhEpo may be used, which takes the place of the cat's natural erythropoietin and enables the bone marrow to continue to make red blood cells. Common trade names are Epogen, Procrit or Eprex.
The manufacturers of Epogen also make another type of human erythropoietin called Aranesp (darbepoetin alfa), and recently some people have been using this on their anaemic cats instead of Epogen, Procrit or Eprex. See below for more information.
Any of these products may be used for cats with severe CRF-related non-regenerative anaemia. In order to avoid confusion with the different trade names, the term rhEpo (recombinant human erythropoietin) will be used in this section.
RhEpo is an extremely effective drug, but unfortunately, there is one major disadvantage to using it. RhEpo is a human version of erythropoietin, manufactured from human DNA. As a result, some cats will eventually produce an antibody reaction to the drug because their bodies consider it to be a foreign body. It is not known for certain how many cats go on to develop this antibody reaction because it is hard to test for this; but Dr Katherine James, a feline kidney specialist, took part in the 1998 clinical trials on the use of rhEpo in cats (Cowgill LD, James KM, Levy JK, Egrie JC, Browne JK, Miller A, Lobinger R: Use of recombinant human erythropoietin for management of anaemia in dogs and cats with renal failure Journal of the American Veterinary Medical Association 212 pp521-8), and in those trials the number of cats who developed the reaction was around 30%. However, on the Feline CRF Information and the Anaemia list, the frequency of the antibody reaction in practice appears to be far lower than 25-30%, perhaps closer to 5-10%. See below for a possible explanation of this discrepancy.
Whatever the actual percentage, as a result of this risk it is usually recommended that cats should not be placed on rhEpo until the benefits of using the rhEpo are thought to outweigh the risks - for most cats this means once their PCV has fallen to 15-19%. In theory, this will often not happen until the CRF is fairly well advanced with creatinine levels over 500 (US: 5.65), although this is not always the case - Thomas needed rhEpo regularly when his creatinine level was only 316 (US: 3.57).
It is impossible to predict which cats will develop the antibody reaction, although a recent report from Janssen-Ortho, the manufacturers of Eprex, indicates that Eprex appears to carry a higher risk of the antibody reaction for humans than either Epogen or Procrit, particularly if the HSA-free form of Eprex (which contains polysorbate 80 instead of albumin, in order to comply with European requirements) is used. Erythropoietin-associated PRCA: still an unsolved mystery (2006) Schellekens H, Jiskoot W Journal of Immunotoxicology 3(3) pp123-130 reports further on this issue.
The reaction does not usually occur in the first month of use, and if it is going to occur it almost always happens around 4-5 months of commencing treatment (only rarely does it happen much earlier or later than this). There is no definitive test to show that the cat has developed the antibody reaction; a bone marrow aspiration would provide some information, but is invasive and unlikely to be worthwhile. Washington State University has some information on this procedure.
From a practical perspective, the main sign of an antibody reaction is that the cat's PCV value will steadily drop by approximately 2-3% a week, despite the use of adequate amounts of rhEpo. Large drops in PCV in the space of a few days or a week are very unlikely to be caused by the antibody reaction, and other possible causes such as gastro-intestinal bleeding should be investigated.
Note the use of the word "adequate": to complicate matters further, your cat may actually need more rhEpo than you have been giving: many vets give a too small dose in the mistaken belief that this may reduce the risk of the antibody reaction. Plus some cats simply need more Epogen than others - Thomas's PCV went up and down in the first few weeks of treatment so we were very worried, but we simply gave him more rhEpo rather than less, and his PCV then rose steadily. A cat whose CRF is advancing may also need more rhEpo than s/he previously needed. A cat who appears not to be responding to rhEpo may also need more iron. If for some reason you are using the 10,000 strength and above, be aware that the rhEpo may lose its potency before you get a chance to finish the vial. This can lead you to incorrectly suspect that your cat is developing the antibody reaction.
So if PCV levels do begin to fall, you should not automatically fear the worst, but instead should consider all other possible causes of the fall.
One other issue which I am asked about occasionally relates to a warning issued by the US Food & Drug Administration in 2007. This was in connection with using rhEpo in humans, and it recommends aiming for lower target haemoglobin levels than many doctors originally aimed for, because this reduces the risks of serious side effects. However, it has always been recommended that people aim for a conservative HCT level of no more than 35% in cats using these products, so I do not think this warning raises any additional concerns at this time.
Why the Antibody Risk is Not as Bad as it Sounds Whilst nobody wants their cat to experience the antibody reaction, it must be stressed that it is not as awful as it sounds. Some people think it is akin to anaphylactic shock but it is nothing like that at all! All that happens is that the PCV gradually falls at a rate of 2-3% a week (any larger fall and you should search for another cause, such as gastro-intestinal bleeding), despite the cat being on rhEpo. If the cat is still producing a little erythropoietin naturally, the antibodies may also neutralise the cat's own erythropoietin as well, at least for a while, and this further worsens the anemia. Since the resulting anaemia will eventually kill the cat, the only remedy is to stop using rhEpo. But the cat was already suffering from severe anaemia, otherwise rhEpo would not have been started in the first place. So in the worst case, using rhEpo will have bought you an extra few months with your cat; and in the best case, using rhEpo could control your cat's anaemia indefinitely.
But, and most importantly, even in those cats who develop the antibody reaction, the rhEpo antibodies will not always neutralise the effects of the rhEpo. In other words, some cats may have the antibody reaction but you would never know it because the rhEpo continues to work and the cat does not become anaemic again. This may explain why it is often claimed that 30% of cats develop the antibody reaction, yet in practice on the Feline CRF and Anaemia Lists, the percentage appears to be much lower, around 5-10%.
This is not to minimise the stress of making the decision to use rhEpo. I know it is not easy. However, since the alternative to starting rhEpo is to watch your cat die of anaemia, to some extent there is no real decision to make, particularly since if you wait too long before starting rhEpo, your cat may die of the anaemia before the rhEpo has a chance to take effect (it may take up to two weeks to see an improvement after starting to use rhEpo). We decided to use rhEpo because, firstly, it was quite obvious that if we did not do so, the anaemia would kill Thomas long before the CRF would (he was very weak); and secondly, we felt the odds were in our favour with at least a two to one chance that it would work for us.
If you are considering the use of rhEpo, don't take too long to make your decision. Because non-regenerative anaemia caused by CRF tends to develop and worsen gradually many cats' bodies do adapt to the anaemia, so they may not seem desperately ill but could still be heading towards a crisis should the PCV fall too low. Plus once you begin rhEpo, it takes a couple of weeks to start taking effect, and even then the PCV should only increase by 2% a week, so if you wait too long your cat could die of anaemia before the rhEpo can help. In such cases a blood transfusion might tide your cat over through the critical period.
Personally I would never let PCV fall below 15% before starting rhEpo, and if my cat was showing symptoms of anaemia with a PCV of 16-20%, I would start it earlier.
So, to summarise:
Ultimately it is your decision whether to use rhEpo. There have been trials into feline alternatives (see alternatives to human erythropoietin) but, according to the researchers involved, neither of these studies is expected to result in the commercial availability of alternative treatments in the foreseeable future.
Why Stopping and Starting Epogen is a Bad Idea Very occasionally, it is possible to stop giving rhEpo completely. In fact, if your cat has acute renal failure rather than CRF, you may not need to start it in the first place - although cats with ARF tend to have high bloodwork results generally, they often are not anaemic, or, if they are, the anaemia resolves itself naturally as the kidneys begin working again.
However, I have heard that some vets have a policy for every CRF cat they treat of using rhEpo short-term until the anaemia is resolved, then stopping it and starting it again later when the cat has become anaemic again, in the mistaken belief that this may reduce the risk of the antibody reaction.
This is really not a good idea. Dr Kathy, who participated in the Epogen trial in cats mentioned above (the trial that has many vets worried about the antibody reaction in the first place) has stated that there is no evidence either way, but she suspects that doing this might actually increase the risk of the antibody reaction occurring. She also believes that the resulting fluctuations in PCV could cause problems with blood pressure control.
On the most basic level, I really do not see the point of allowing a cat to become anaemic again, with all the strains on the body and effects on the cat's quality of life which that entails. In addition, I heard from one person whose vet insisted on this approach and whose cat died from anaemia during one of his anaemic phases. If you decide to use rhEpo, I'd recommend making a commitment to using it fully in order to keep your cat completely free of anaemia.
Dosage and Usage Guidelines for Epogen, Procrit or Eprex
I suggest you read this entire section in order to familiarise yourself with how to give rhEpo. Topics covered include: RhEpo is available in various strengths but you do not want the 10,000iu and higher strengths, because it is too hard to obtain cat-sized doses from these. In the USA the strengths most commonly used for cats are 2,000iu and 3,000iu, but in the UK and Canada you may be offered the 1,000iu strength, which confusingly is the same as the 2,000iu strength, but half the amount. Obviously, if you are using a lower strength, you need to give more of it. Your vet should be able to advise you on which strength to buy. Click on the country you are interested in: In the UK, if your vet doesn't have it in stock, rhEpo (trade name Eprex) is available from pharmacies, although you will need a prescription from your vet, and the pharmacy may have to order it in for you (usually it can be delivered in a day or two). It costs around £90 for six syringes, which is the equivalent of 12-24 treatments for most cats. One lady wrote to tell me that she was able to obtain Eprex very quickly from her local hospital pharmacy, with a prescription from her vet, of course.
In the USA, it is often possible to obtain the US version of rhEpo, Epogen, by mail order (with a prescription), although you have to be very careful about it being refrigerated during shipping.
Some of the pharmacies below offer family savings plans whereby you pay an annual membership fee and then receive a discount on the price of your prescription medications. These schemes often permit cats to be enrolled as family members, which may further reduce your costs.
If you don't want to order online, some local pharmacies in the USA, such as Walgreens, can order Epogen with overnight delivery for around US$30-35 per 2,000iu vial. Hospital pharmacies often have Epogen in stock and may well be prepared to sell it to you with a prescription.
You will probably also need U100 insulin 0.3 or O.5cc syringes, which cost around US$15 per hundred (Brico Medical sells 100 Terumo syringes for around this price though you will need a prescription). You can also obtain insulin syringes from your local pharmacy. Since we used Eprex, we did not need insulin syringes, instead we used the syringe and needle in which the Eprex came, giving half the vial each time. The Obtaining Supplies Cheaply page also has information about obtaining supplies cheaply, including links.
I am not aware of any suppliers in Canada, though Eprex is certainly used there, and should be available from local pharmacies, particularly hospital pharmacies. If you cannot find a Canadian supplier, Entirely Pets in the USA sells Epogen for US$45.99 for a vial of the 2000iu strength and will apparently ship to Canada.
You should check with your vet on the appropriate dosage for your cat. For reference, The Veterinary Drug Handbook (4th edition) (2002) by Donald C Plumb suggests using 100 units of rhEpo per kg (2.2lbs) of cat, given sub-cutaneously three times a week until you begin to approach the target PCV level (usually around 35%).
Some cats may require higher doses initially, particularly cats with severe anaemia. Plumb's suggests using up to 145 units per kg (2.2lbs) of cat, also given sub-cutaneously three times a week, if anaemia is severe (PCV or HCT below 14%). Even if your cat does not have severe anaemia, discuss this possibility with your vet if your cat does not appear to respond to the treatment.
However, a lower dose of 48.4 units per kg (2.2lbs) of cat, sub-cutaneously three times a week, may be advisable if the cat has hypertension (high blood pressure) before starting rhEpo.
The exact amount of rhEpo to be given depends upon the strength which you are using. RhEpo is sold in varying strengths, but the larger sizes (10,000iu/mL upwards) are impossible to give in cat-sized amounts, so try to use nothing larger than the 3000iu/mL strength. If for some reason you do end up using the 10,000 strength and above, be aware that the rhEpo may lose its potency before you get a chance to finish the vial. This can lead you to incorrectly suspect that your cat is developing the antibody reaction.
Calculating how much rhEpo to use can be very confusing! Normally you will be told how many units to give, based on your cat's weight. 1 cc of the 3000iu/mL strength contains 3000 units of rhEpo; 1 cc of the 2000iu/mL strength contains 2000 units of rhEpo; and so on. We used the 1000iu strength, which (just to confuse matters) is slightly different: it contains 1000iu but in 0.5mL so it is the same strength as the 2000iu/mL although it sounds different. Whichever you use is less important than giving the correct amount of rhEpo.
If you are using Epogen or Procrit, you will probably also need U100 insulin 0.3 or O.5cc syringes (see above for sources). To complicate matters even further, insulin units are not the same as Epogen units. However, 1 insulin unit is 0.01cc; so each unit on an insulin syringe is 0.01cc, which should help you when you come to measure out the dose. I would still recommend asking your vet to show you exactly how much to draw up though.
As you can see, the dosages below are pretty precise, but your vet will probably want to round the dose up or down so as to make it easier for you to measure it.
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
