Teratogen Update: Reproductive Risks of Leflunomide (AravaTM); A Pyrimidine Synthesis Inhibitor: Counseling Women Taking Leflunomide Before or During Pregnancy and Men Taking Leflunomide Who Are Contemplating Fathering a Child

AravaTM (leflunomide) is a pyrimidine synthesis inhibitor used in the treatment of active rheumatoid arthritis (RA). The chemical name for leflunomide is N-(49-trifluoromethylphenyl)-5-methylisoxazole-4-carboxamide. Because the drug has been successful in the treatment of rheumatoid arthritis, it is being widely prescribed. In spite of the clear warning that the drug should not be prescribed for pregnant women, approximately 30 women have become pregnant while taking leflunomide as of December 1999. This commentary was prepared to aid teratology counselors and genetic counselors who might be contacted by physicians or patients about the risk of leflunomide exposure during pregnancy. Before the subject of risk is discussed, it is important to understand the results of preclinical testing, phamacokinetic studies, and clinical studies that are available.