Frequently Asked Questions About Leukeran (chlorambucil)
By Rebecca Kimsey

1) What is Leukeran? Leukeran is the brand name for (generic) chlorambucil. It is an immune system suppressing drug given to dogs or cats for immune-mediated disorders such as cancer, including leukemia and lymphoma. It is also used as a treatment for severe non-responsive Inflammatory Bowel Disease (IBD). Note: in this FAQ the term Leukeran is used, but except where noted, the discussion applies equally to chlorambucil.

2) Why give Leukeran? If your kitty has been diagnosed with small-cell lymphoma, Leukeran is a proven, effective treatment that is very well tolerated by cats. It can put your cat into remission from this cancer. It is also prescribed for severe non-responsive IBD as an immune system suppressant with strong anti-inflammatory properties. https://www.ibdkitties.net/ibd-or-cancer/

3) Leukeran is a chemotherapy drug. It sounds dangerous, is it? Any medication has risks. It is true that Leukeran is a powerful drug, but careful handling as discussed below, and washing your hands are the usual precautions.

4) How is Leukeran given? It is an oral medication. It is a brown tablet (Leukeran), or compounded into pills, capsules or liquid medication as chlorambucil.

5) What is difference between Leukeran and chlorambucil? Which should I give? The brand name of the medicine is Leukeran; it’s a small brown 2mg tablet. The company that manufactures Leukeran does not produce the generic. This is why the generic, chlorambucil, is a compounded drug. Legally, compounding pharmacies may not produce a 2mg dose. This is why chlorambucil may be in doses of 1.9mg or 2.1mg, and may be compounded as a tablet, capsule or oral medication.

6) Does it only come in pill form? Leukeran is only available in 2mg brown tablets. The compounded chlorambucil can be made as pills, capsules or liquid.

7) How much does Leukeran cost? In the U.S., Leukeran is very expensive, at about $26 to $28 per pill. The compounded generic is more reasonably priced; many use chlorambucil instead of Leukeran because of the cost. Leukeran in other countries (such as Canada) has run about the same price as chlorambucil in the U.S. Some vets will insist on the brand drug (Leukeran) due to concerns about compounding inadequacies, but we are not aware of any reported problems with the compounded form.

8) What about my other pets? Just keep the litter box clean, and if you have a dog, do make sure they don’t eat the poop. That’s all that’s needed. Cats can groom each other, you, etc. No special precautions other than perhaps scooping more than you normally do. The usual recommendation is 2x a day. As people with IBD cats, we assume that all of us scoop at least that often.

9) Do I have to take special precautions? Generally wearing gloves when giving the dose, and regular, thorough hygiene and hand washing are adequate and the normal precautions. Some vets warn against touching urine, feces, saliva; others don’t even tell you to wear gloves when giving the dose. But who among us gets poop or urine on our hands and doesn’t wash up right away? Of course, if you are immune compromised yourself, you may need to take extra precautions. Please discuss with your vet.

10) What dose of Leukeran should I give my cat, and how often? Your vet will determine the dose and the frequency of delivery. The most typical dosage has been 2mg every other day. There are variations in frequency including every second or third day, to a much higher dose (approximately 6mg) given approximately twice a month (which works out to a lower overall dose). Some cats are started on the more frequent dose, then switched to the twice a month dose.

11) How long will I give Leukeran? Your vet will advise you. Kitties in the IBDKitties support group have been on the medication for a year or longer. When used for small cell intestinal lymphoma, some cats are put on it for life; some oncologists prescribe it only until kitty is determined to be in remission. When used for severe IBD, it ranges from short to long term, depending on your cat’s response and need.

12) What can I expect when my kitty first starts taking Leukeran? What are the side-effects and will my kitty have the same kind of problems that humans on chemotherapy do, such as hair loss, nausea, lack of appetite? Leukeran is usually very well tolerated. Only about 15% of cats experience side-effects that result in discontinuing its use. As with all chemotherapy in cats, the approach is focused on quality of life, and thus dosages are much lower than human equivalents, minimizing potential side-effects. The experiences of pets on chemotherapy cannot be compared to experiences of humans for this reason. The most common side effects can be lethargy, lack of appetite, nausea or vomiting; diarrhea is possible, though often diarrhea is already present prior to treatment. These symptoms may occur at the start of treatment, and ease over time. And of course, some of the symptoms are the same we face with IBD or pancreatitis. Your cat will need to be monitored for the drug’s impact on bone marrow, as bone marrow suppression is possible. This can result in anemia, or depressed white blood count, or changes to other blood enzymes. If this happens, the treatment is stopped until the bone marrow responds, usually within a few weeks at most, and then kitty can resume the treatment.

13) What can help with the side effects? Just as in IBD or other gastro-intestinal issues with our kitties, anti-emetics, anti-nausea, anti-acids, and appetite stimulants can be essential tools in combating vomiting or lack of appetite. Canna Companion has helped some kitties as well.

14) I’ve heard that it’s necessary to regularly do blood tests when cats are on Leukeran. Why? As mentioned, one of the possible side-effects of the chemotherapy is bone marrow suppression. This can lead to anemia, and that can be fatal if not monitored and managed. Thus, it is necessary to do regular CBC (Complete Blood Count) testing to measure any change to Red Blood Cells, White Blood Cells and Hematocrit (RBC, WBC, HCT). A sudden, lasting drop in the HCT will mean that Leukeran will be stopped, at least temporarily. Your vet should advise a regular schedule to do the CBC. It may range from weekly or bi-weekly in the beginning, to monthly, or some similar schedule. If your vet does not tell you, be sure to discuss the need for regular and on-going monitoring.

15) Is Leukeran all the medicine that my kitty will need to take? If not, what others are given? A steroid such as prednisolone is usually prescribed in conjunction with Leukeran, and often at a higher dose than normally prescribed for IBD. Other steroids can be used. A possible regimen might be 2mg Leukeran every other day with 10mg prednisolone daily. The purpose of this is to aid in immune system suppression and combat inflammation associated with bowel disease, or cancer. Your vet should discuss with you the drugs used to combat the IBD or lymphoma, as well as any other supportive meds. These might include those for nausea, vomiting, inappetence – which we are familiar with from IBD or pancreatitis. https://www.ibdkitties.net/introduction-to-steroids-4/

16) Does Leukeran cure lymphoma or severe IBD? Leukeran does not cure IBD. The practical experience with use of Leukeran in the treatment of small cell intestinal lymphoma diagnosed via biopsy is that 85% of the time, Leukeran puts kitty into remission.

17) Is special handling necessary? Leukeran MUST be kept refrigerated. It cannot be cut or crushed. Avoid contact with the medication. Wear gloves when administering the dose.

18) Do you have to have a biopsy diagnosis in order to start Leukeran? In our experience, this will vary. A vet who isn’t familiar with your kitty is far more likely to insist on a biopsy. If the vet has been treating your kitty for considerable time and is therefore more familiar with kitty’s history, especially if there have been previous ultrasounds or biopsies, they should be more willing to start Leukeran without a confirming biopsy. Some vets will not give the drug, perhaps for legal reasons in some states, and will instead refer you to an oncologist or internal medicine specialist for treatment. These new doctors may or may not want a biopsy done. Be aware that if your kitty is on a steroid, she will need to be slowly tapered off the steroid for a biopsy to be worthwhile. Note that a biopsy is the best method of determining if your kitty’s bowel issues are from IBD, or from lymphoma, or other cancer. If cancer, the most common type is small-cell lymphoma, which responds very well to Leukeran, just as IBD does. If it’s large-cell lymphoma, then a completely different chemotherapy protocol is required.

19) My vet hasn’t mentioned Leukeran. What can I do? Ask the vet about using it. I suggested it to my vet for my Boston. My vet had no experience with it in cats, but did discuss with our internist, and they agreed it was time to start Leukeran. Some vets have no experience with it, particularly in cats. There are Case Studies on the IBDKitties website about cats who have been on Leukeran (see below).

20) My vet still doesn’t want to give it, but I think it may be necessary. What can I do? Discuss further as to why your vet doesn’t want to give it. If it’s due to their lack of experience with this protocol, ask if they would consult with a specialist (internist, oncologist) who does have the experience. If they won’t do that, and you do want to pursue this treatment, then consider either going to another local vet, or to a specialist. Ask for a referral for a specialist from your vet. Or ask in the group, or look at the AAVA website for specialists or vets in your area.

21) Case Studies – IBDKitties website:

22) How long before I can expect to see any results? That, of course depends on what is wrong with your kitty, how severe the condition is, the overall health of your kitty, plus how well they respond to the drugs given: Leukeran, prednisolone. Many kitties on Leukeran have severe diarrhea as a symptom of their illness (whether IBD or SC lymphoma). Some kitties have seen formed stool within the first week; others have taken four to six weeks before reaching that point, although associated foul smell and/or pale color tend to improve earlier. Please note that if you are not already giving your cat b12 shots, this should also be discussed with your vet, as diarrhea often will not resolve until B12 levels return to normal. https://www.ibdkitties.net/the-importance-of-b12/

23) What if my cat can’t tolerate Leukeran, are there alternatives? Treatment with high doses of steroid alone is one option. Atopica (cyclosporine) is another. They may or may not be effective alone, or together. There may be other alternatives. Talk with your vet.

24) What if I miss a dose? As with human medication, if you miss a dose, give as soon as you realize, UNLESS it is nearly time for the next dose. Do not double up on a dose ever, as this may result in toxicity.

25) What else can I do to support my kitty while on Leukeran?
— Feed the best food you can: https://www.ibdkitties.net/feline-nutrition/
— Give probiotics to help with digestion: https://www.ibdkitties.net/probiotics/
— Ensure adequate levels of B12: https://www.ibdkitties.net/the-importance-of-b12/

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