Leflunomide
Also known as: Arava
- **Experimental Use**: This medication is relatively experimental when used in veterinary patients. Contact your veterinarian immediately if any unusual effects (such as decreased appetite, lethargy, or vomiting) are noted. - **Safe Handling**: This drug is a known teratogen (can cause birth defects). Pregnant women or women trying to conceive should **not** handle this medication. Always wear gloves when handling, and **do not crush or split** the tablets. - **Cost**: Treatment can be very expensive, though prices have decreased with the availability of generic formulations. - **Nursing**: Do not allow nursing pets to feed if the mother is receiving this drug; use milk replacer.
Dosage must be set by your veterinarian for your specific pet. Never give human medication or another pet’s prescription without veterinary guidance.
What it is used for
- Rheumatoid arthritis
- Immunosuppressive as part of a protocol (with cyclosporine) following organ transplant
- Adjunctive immunosuppressive for immune-mediated hemolytic anemia
- Treatment of systemic and cutaneous reactive histiocytosis
- Treatment of Evans' Syndrome in a diabetic dog
How it is given
Possible side effects
- Decreased appetite
- Lethargy
- Vomiting
- Diarrhea
- Lymphopenia
- Anemia
- Alopecia
- Rash
- Hepatotoxicity
- Severe dermatologic reactions (Toxic Epidermal Necrolysis, Stevens-Johnson syndrome - reported in humans)
- Gastrointestinal upset (vomiting, diarrhea, anorexia)
- Bone marrow suppression (leukopenia, anemia, thrombocytopenia)
- Unexplained bleeding
Cautions & contraindications
- Pregnancy (Category X teratogen)
- Hypersensitivity to leflunomide
- Pre-existing immunodeficiency
- Significant renal impairment
- Pregnancy and lactation
- Pre-existing severe bone marrow suppression
- Severe hepatic impairment
- Active severe infections
- **Teratogenicity Warning**: Leflunomide is an FDA Category X teratogen. It must not be used in pregnant animals, and pregnant women should not handle this medication. **Prolonged Half-Life**: The active metabolite (A77 1726) can persist in the body for up to 2 years after discontinuation. If severe toxicity occurs, a washout procedure using cholestyramine or activated charcoal is required. Use with extreme caution in patients with hepatic disease, renal impairment, or pre-existing immunodeficiency.
Drug interactions
- Charcoal, Activated: Can increase elimination and decrease A77 1726 drug concentrations; used for rapid washout.
- Cholestyramine: Can increase elimination and decrease A77 1726 drug concentrations; used for rapid washout.
- Hepatotoxic Agents: Increased risk for hepatotoxicity when used concurrently.
- Methotrexate: Increased risk of adverse effects and elevated ALT.
- Phenytoin: Leflunomide can increase phenytoin levels.
- Rifampin: Can increase A77 1726 peak levels.
- Vaccines, Live Virus: Should be used with extreme caution, if at all, due to immunosuppression.
- Warfarin: Leflunomide may increase INR.
- Other immunosuppressants (e.g., cyclosporine, azathioprine): Increased risk of severe immunosuppression and bone marrow toxicity
- Live vaccines: Risk of disseminated infection due to immunosuppression
Frequently asked questions
What is Leflunomide used for in pets?
- **Experimental Use**: This medication is relatively experimental when used in veterinary patients. Contact your veterinarian immediately if any unusual effects (such as decreased appetite, lethargy, or vomiting) are noted. - **Safe Handling**: This drug is a known teratogen (can cause birth defects). Pregnant women or women trying to conceive should **not** handle this medication. Always wear gloves when handling, and **do not crush or split** the tablets. - **Cost**: Treatment can be very expensive, though prices have decreased with the availability of generic formulations. - **Nursing**: Do not allow nursing pets to feed if the mother is receiving this drug; use milk replacer.
Is Leflunomide safe for my pet?
Dosage must be set by your veterinarian for your specific pet. Never give human medication or another pet’s prescription without veterinary guidance.
This article is for general education and is not a substitute for professional veterinary advice. If your pet is unwell, please consult a veterinarian.
Worried about your pet?
Peqaboo’s AI helps you track symptoms, understand lab reports, and know when to see a vet.
Get the Peqaboo app