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Procarbazine for Dogs and Cats

By Barbara Forney, VMD

Last reviewed: 7/13/2022

Commonly prescribed for: Lymphoma chemotherapy, granulomatous menigoencephalomyelitis

Species: Dogs and Cats

Therapeutic Class: Atypical-alkylating Agent

Basic Information

Procarbazine is a chemotherapeutic drug that is used as a part of the MOPP (mechlorethamine, vincristine, procarbazine, and prednisone) protocol to treat relapsed lymphoma in dogs and cats. There also are studies that indicate that procarbazine may be useful as a sole, long-term treatment for granulomatous meningoencephalomyelitis in dogs.

Procarbazine is an atypical alkylating agent that inhibits RNA, DNA and protein synthesis. It is used in human medicine to treat brain tumors, such as oligodendroglioma and glioblastoma, and Hodgkin's Disease. Based on information extrapolated from human research, procarbazine is well-absorbed orally and equilibrates rapidly between the plasma and cerebral spinal fluid (CSF). Procarbazine is metabolized by the liver and kidney and excreted in the urine. Urinary metabolites are cytotoxic.

Dogs and Cats

Procarbazine is used as a part of the MOPP protocol for relapsed lymphoma in dogs. In one study, which looked at the MOPP protocol in a group of dogs with advanced lymphoma, the median survival with treatment was 10 months. The only prognostic indicator for poor outcome in this group was inappetence. at the time of diagnosis. The majority of dogs tolerated the MOPP protocol well.

The MOPP protocol is used both as first-line chemotherapy and as rescue chemotherapy in cats with lymphoma. Cats that were eating well and not "sick" at the time of diagnosis tended to respond better to chemotherapy.

Procarbazine has been studied as a sole treatment for granulomatous menigoencephalomyelitis (GME) in dogs. GME is the second most-common inflammatory disease of the central nervous system of dogs. It is more commonly seen in toy breeds. Left untreated, the survival time for dogs with GME is less than one month. GME was traditionally treated with prednisone, but recent studies have looked at treatment with procarbazine or cyclosporine. The procarbazine study showed an improved survival time of 14 months.

Procarbazine Side Effects

The most-common side effects are gastrointestinal (GI), including anorexia, vomiting, and diarrhea. In one study, GI toxicity occurred in 28% of treated animals. Bone-marrow suppression, central nervous system (CNS) depression, and peripheral neuropathy are less common but significant side-effects.


  • Wear gloves when handling procarbazine and avoid contact with the animal's saliva and urine due to cytotoxic metabolites.
  • Weekly monitoring of peripheral blood counts, hepatic, and renal function should be performed for the first month of treatment and regularly thereafter.
  • Procarbazine should be avoided or used with extreme caution in animals with pre-existing bone-marrow suppression.
  • Procarbazine should be used with caution in animals with decreased liver or kidney function.
  • Procarbazine should not be used in pregnant or lactating animals. Procarbazine has been shown to adversely affect spermatogenesis. There are studies in the human literature discussing protocols to diminish testicular toxicity.

Drug Interactions

  • Procarbazine should be used only with extreme caution with other CNS depressant drugs, including barbiturates, opiates, antihistamines, and tranquilizers.
  • Procarbazine should not be used with tricyclic antidepressant drugs or sympathomimetics. Ingestion of alcohol may cause severe nausea and vomiting.
  • Animals receiving procarbazine should not be fed foods with high tyramine content (yogurt and some cheeses) due to adverse effects on blood pressure.


Overdose with procarbazine should be treated aggressively. If recognized promptly, gut-emptying protocols should be employed. Supportive care for GI upset, bone-marrow suppression, and CNS depression may be warranted.
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