Introduction

Name

• Leflunomide.

Class of drug

• Immunosuppressant.

Description

Chemical name

• 5-methyl-N-[4-(trifluoromethyl)phenyl]-1,2-oxazole-4-carboxamide.

Molecular formula

• C₁₂H₉F₃N₂O₂

Molecular weight

• 270

Physical properties

• Occurs as a white or almost white powder. Poorly soluble in water.
• Available as tablets for oral administration as an authorised human medicine.

Storage requirements

• Store at room temperature and protect from light.

Uses

Indications

• Has been used in dogs to treat immune-mediated blood disorders (eg primary immune-mediated hemolytic anemia Anemia: immune mediated hemolytic, immune-mediated thrombocytopenia Immune-mediated thrombocytopenia, Evans’ syndrome), systemic and cutaneous reactive histiocytosis Reactive (systemic and cutaneous) histiocytosis, immune-mediated polyarthritis Arthritis: immune-mediated and inflammatory rectal polyps. 
• Has been used with methotrexate to treat rheumatoid arthritis in cats.

Administration

Pharmacokinetics

Precautions

Interactions

With other drugs

• There may be an increased risk of adverse effects in the case of recent or concomitant use of hepatotoxic or hematotoxic drugs.
• P450 (CYP) 1A2, 2C19 and 3A4 isoenzymes may be involved in leflunomide metabolism, which may lead to interactions with drugs that affect, or are affected by these isoenzymes.

Adverse Reactions

Further Reading

Publications

Refereed Papers

• Recent references from PubMed and VetMedResource.
• Tani A et al (2020) Comparison of the efficacy of cyclosporine and leflunomide in treating inflammatory colorectal polyps in miniature dachshunds. Vet Med Sci 82,  4437-4440 PubMed.
• Weingart C et al (2019) Primary immune-mediated haemolytic anaemia: a retrospective long-term study in 61 dogs. Aus Vet J  97, 483 PubMed.
• Sato M et al (2017) A retrospective study of the safety and efficacy of leflunomide in dogs. J Vet Intern Med 31, 1502-1507 PubMed.
• Mehl M L et al (2012) Pharmacokinetics and pharmacodynamics of A771726 and leflunomide in domestic cats. J Vet Pharmacol Ther 35, 139-146 PubMed.
• Singer L M et al (2011) Leflunomide pharmacokinetics after a single oral administration to dogs. J Vet Pharmacol Ther 34, 609-611 PubMed.
•  Colopy S A et al (2010) Efficacy of leflunomide for treatment of immune-mediated polyarthritis in dogs: 14 cases (2006–2008). JAVMA 236, 312-318 PubMed.
• Hanna F Y (2005) Disease modifying treatment for feline rheumatoid arthritis. Vet Comp Orthop Traumatol 18,  94-99 PubMed.

Organisation(s)

• Electronic Medicines Compendium (eMC): www.medicines.org.uk