Melphalan is a chemotherapy tablet given at home, and it is the backbone of treatment for multiple myeloma in dogs, usually paired with the steroid prednisone.1PubMed Central. Comparison of two melphalan protocols and evaluation of outcome and prognostic factors in multiple myeloma in dogs For this cancer it tends to work well, often turning a serious diagnosis into one that many dogs live with for a long time. Its main cost is quiet rather than obvious, since it can lower the blood cells the bone marrow makes, which is why treatment comes with routine blood tests. The drug also passes into a treated dog’s saliva and waste, so living with a dog on melphalan means some new household habits too.2British Small Animal Veterinary Association. Melphalan Client Information Leaflet
What Melphalan Treats and How Well It Works
Multiple myeloma is a cancer of plasma cells, the bone marrow cells that normally make antibodies. The cancerous cells flood the blood with one abnormal protein, which can thicken the blood, weaken immunity, or damage organs.3allvetslink.com. Canine Multiple Myeloma Melphalan damages the DNA of dividing cells at any stage of their growth cycle, which is why it can slow these cancer cells.4PubMed Central. Comparison of two melphalan protocols and evaluation of outcome and prognostic factors in multiple myeloma in dogs
With daily melphalan and prednisone, about 9 in 10 dogs with myeloma respond, and half live longer than about a year and a half (540 days).5PubMed Central. Comparison of two melphalan protocols and evaluation of outcome and prognostic factors in multiple myeloma in dogs In a newer comparison of two melphalan schedules, half the dogs lived longer than about 2.5 years (930 days).6PubMed Central. Comparison of two melphalan protocols and evaluation of outcome and prognostic factors in multiple myeloma in dogs With a 10-day cycle schedule, about 3 in 4 dogs responded and half lived longer than about 17 months.7PubMed. Cyclical 10-day dosing of melphalan for canine multiple myeloma The studies enrolled different dogs, used different schedules, and defined response in slightly different ways, so the figures shouldn’t be lined up as if one beat the others.
For myeloma, response usually means the abnormal protein in the blood falls, which your vet follows with repeat bloodwork rather than by how your dog looks. A partial response means the protein has dropped substantially but not disappeared, and that still counts as treatment working.
Median survival means half the dogs lived longer and half shorter, not a fixed lifespan. Your vet can see your dog’s bloodwork, protein level and overall health, and that picture should guide your expectations more than any published average.
Relapsed lymphoma is a secondary use. For lymphoma that has come back after earlier chemotherapy, melphalan on its own gave limited, short-lived benefit, though dogs tolerated it well.8PubMed. Oral melphalan for the treatment of relapsed canine lymphoma In a four-drug rescue combination that includes melphalan, about 4 in 10 dogs with relapsed lymphoma went into remission, but the cancer typically returned within about 3 to 4 weeks.9PubMed Central. The efficacy and adverse event profile of dexamethasone, melphalan, actinomycin D, and cytosine arabinoside (DMAC) chemotherapy in relapsed canine lymphoma Relapsed lymphoma is usually aggressive and harder to control with any drug, so melphalan is a later-stage option to buy time rather than a long-term control.
How Melphalan Is Given at Home
Melphalan is swallowed as a tablet and absorbed from the gut quickly, reaching its peak in the blood within about 30 minutes.10PubMed. Pharmacokinetics of the absorption, distribution, and elimination of melphalan in the dog Tablets should be given whole and never split or crushed.11British Small Animal Veterinary Association. Melphalan Client Information Leaflet If a dose doesn’t divide evenly, ask your vet or pharmacy for a different strength or a compounded form rather than cutting pills.
Some dogs take a small dose every day, while others get a larger dose on a few days followed by a break.12PubMed Central. Comparison of two melphalan protocols and evaluation of outcome and prognostic factors in multiple myeloma in dogs A pulse schedule is often used when daily dosing has driven down the dog’s clotting cells.13PubMed Central. Comparison of two melphalan protocols and evaluation of outcome and prognostic factors in multiple myeloma in dogs The two schedules were similarly well tolerated and similarly effective for myeloma.14PubMed Central. Comparison of two melphalan protocols and evaluation of outcome and prognostic factors in multiple myeloma in dogs
Wear gloves to handle the tablet, and give it whole in a bit of food or a pill pocket so the dog swallows it without chewing. Give the dose at the same time each day or on the same scheduled days, and write each one down so nobody in the household gives it twice or skips it. If a dose is missed or the dog vomits after taking it, call your vet for instructions instead of giving an extra tablet to catch up, since the drug’s main risk is a dose that is too high. Keep the tablets in the labeled container, out of reach of children and other pets.
Prednisone, the steroid often paired with melphalan for myeloma, commonly increases thirst, urination and appetite, so expect more trips outside and a hungrier dog. Never stop it suddenly without your vet’s guidance.
Side Effects to Watch For
The most common side effect of melphalan is suppression of the bone marrow, which makes blood cells. Counts of neutrophils, the infection-fighting white blood cells, and platelets, the clotting cells, can drop.15PubMed. Unexpected toxicity associated with use of body surface area for dosing melphalan in the dog The drop in clotting cells can show up later than other effects, which is one reason schedules get adjusted.16PubMed Central. Comparison of two melphalan protocols and evaluation of outcome and prognostic factors in multiple myeloma in dogs In one reported case, two weeks into treatment a dog became tired and stopped eating, and its infection-fighting cells and clotting cells had fallen to dangerously low levels.17PubMed Central. Case Report: Modified pulse-dose melphalan therapy for canine colorectal extramedullary plasmacytoma with suspected hepatic dissemination following surgical excision
Low counts often cause no visible signs, which is the main reason regular blood tests matter. When a problem does show, it tends to look vague: tiredness, a dog who turns away from food, or a general sense that something is off, so a change in energy or appetite deserves a call.
When infection-fighting white blood cells run low, the body has less defense, and a fever, shivering or sudden lethargy can be the first sign. Call your vet the same day, because infection in a dog with low counts can worsen quickly. Don’t wait to see whether it passes overnight, and don’t give human fever medicine without asking, since some are harmful to dogs.
When clotting cells run low, small red or purple spots can appear on the gums or on the thin skin of the belly, and bruises may appear without any injury. Nosebleeds, blood in the urine, or blood in the stool also suggest a clotting problem and warrant a prompt call.
Some dogs have mild stomach upset or a smaller appetite, and vomiting or diarrhea that lasts more than a day should be reported rather than waited out. Hair loss is less common in dogs than in people on chemotherapy, so a normal-looking coat doesn’t mean the drug isn’t affecting your dog. Small dogs can be more sensitive: with intravenous melphalan dosed by body size, about 9 in 10 dogs under 14 kg (about 30 lb) had severe drops in blood counts, versus about 1 in 4 larger dogs.18PubMed. Unexpected toxicity associated with use of body surface area for dosing melphalan in the dog
Kidney disease slows how fast the body clears melphalan, keeping it in the blood almost twice as long.19PubMed Central. Effect of renal dysfunction in dogs on the disposition and marrow toxicity of melphalan Because of this, vets may start dogs with severe kidney disease at about half the usual dose and raise it slowly if tolerated.20PubMed Central. Effect of renal dysfunction in dogs on the disposition and marrow toxicity of melphalan In dogs given monthly intravenous doses for up to three courses, there was no sign of building bone marrow damage, even with reduced kidney function.21PubMed Central. Effect of renal dysfunction in dogs on the disposition and marrow toxicity of melphalan
Blood Tests and Monitoring During Treatment
The main test is a CBC, or complete blood count, which counts the white cells, red cells and platelets in a blood sample. A typical schedule is a blood count every two weeks for the first two months, then once a month.22IDEXX Laboratories. Multiple myeloma case study: Sydney For myeloma, the vet also tracks the abnormal blood protein to see whether the cancer is responding.23PubMed. Cyclical 10-day dosing of melphalan for canine multiple myeloma A falling level suggests it is, while a level that stops falling or starts rising can be an early sign the plan needs adjusting. Your vet may also repeat urine tests and a blood calcium check, because both relate to how myeloma is behaving.
A recheck is usually quick: a small blood sample is taken, often from a leg vein, and many clinics can report results the same day. Before you go, jot down any change in appetite, energy, thirst, or bathroom habits since the last visit, since small details help your vet read the numbers. Ask whether to give the next dose before the results come back or wait for them, because the answer depends on your dog’s schedule and recent counts.
If counts drop or side effects appear, your vet may delay treatment or lower the dose.24ImpriMed. Melphalan: An Overview Your vet may hold a dose for a week or so and recheck, then restart at the same or a lower dose once counts recover.
Progress shows up outside the lab too. Improved energy and appetite often accompany a good response, while returning thirst, weakness, or lameness can signal the cancer coming back.
Handling Tablets and Waste Safely at Home
Wear disposable gloves whenever you handle melphalan and wash your hands with soap and water afterward.25PetMD. Melphalan for Dogs and Cats If the medicine touches your skin, wash it off right away and call your doctor or Poison Control.26PetMD. Melphalan for Dogs and Cats Melphalan and its byproducts appear in a treated dog’s saliva, vomit, urine, stool and blood, so don’t let your dog lick your hands or face during treatment.27PetMD. Melphalan for Dogs and Cats28British Small Animal Veterinary Association. Melphalan Client Information Leaflet
Have your dog toilet away from other pets and people.29British Small Animal Veterinary Association. Melphalan Client Information Leaflet Pick up stool with gloves, seal it in a plastic bag, and dispose of it as your vet instructs.30PetMD. Melphalan for Dogs and Cats Cats on melphalan need the same care with litter.31PetMD. Melphalan for Dogs and Cats
For urine, vomit or stool indoors, put on disposable gloves, soak up the mess with disposable towels, and seal the used towels and gloves in a plastic bag. Wash the area afterward with soap and water, and wash your hands when you finish. Take the same care with spills of blood or saliva.
Pregnant people, those trying to conceive, and children should stay out of handling the tablets, the dog’s waste, and any cleanup, since this is a chemotherapy medicine. Ideally one healthy adult takes on all the medication and cleanup, so exposure is limited to one person who knows the routine. If you’re unsure whether someone in your home should be handling things, ask your vet or your own doctor.
What Affects How Long a Dog Does on Melphalan
Dogs whose myeloma responds to treatment live significantly longer than those that don’t, so how the first weeks and months go tells a lot about the road ahead.32Journal of the American Veterinary Medical Association. Prognostic factors for multiple myeloma in the dog On the 10-day schedule, reaching a full or partial response was tied to longer survival.33PubMed. Cyclical 10-day dosing of melphalan for canine multiple myeloma It is still a group pattern. A dog without an early response may do reasonably well, and one with a response may relapse.
High blood calcium and certain abnormal proteins in the urine were linked to shorter survival.34Journal of the American Veterinary Medical Association. Prognostic factors for multiple myeloma in the dog These are signs of a more difficult case rather than causes you can fix at home, though high calcium can make a dog feel unwell, so your vet may treat it directly alongside the cancer. Detached retinas at diagnosis were linked to survival as well, and a sudden change in vision or eye appearance is worth reporting right away.35PubMed. Cyclical 10-day dosing of melphalan for canine multiple myeloma
Ask which of these factors your dog had at diagnosis, since many dogs have none of them. A poor early response may lead your vet to change the plan, such as the schedule or the drugs, rather than waiting longer, so ask when they would reassess.
Medicines That Can Interfere With Melphalan
Tell your vet about every drug and supplement your dog takes before starting melphalan.36ImpriMed. Melphalan: An Overview | ImpriMed Drugs that suppress the immune system, such as azathioprine, or other bone-marrow-suppressing drugs can add to its effects.37ImpriMed. Melphalan: An Overview | ImpriMed Some antibiotics and antifungals, including chloramphenicol and amphotericin B, are listed as possible interactions.38ImpriMed. Melphalan: An Overview | ImpriMed Check with your vet before any new medication, even for an unrelated problem.
At an emergency visit or any appointment with a different vet, say clearly that your dog is on chemotherapy, since that vet may not have the records. Over-the-counter products, supplements and herbal remedies count as medicines too, so list them even if they seem harmless. Ask when vaccines should be given, since immunity may be lowered during treatment and your vet can decide on the timing.