Leflunomide Toxicity Profile

Introduction to Leflunomide Toxicities

• Leflunomide toxicities primarily affect the gastrointestinal system, liver, bone marrow, and skin, with potentially severe hepatotoxicity being the most concerning adverse effect requiring careful monitoring 1, 2, 3

Common Gastrointestinal Toxicities

• Most common adverse effects include nausea, diarrhea, loss of appetite, weight loss, and dyspepsia 2, 3
• Gastrointestinal irritation is predominant among leflunomide's toxicity profile and often occurs early in treatment 1

Hepatotoxicity

• Severe liver injury can occur and may be fatal in rare cases 3
• Most cases of severe hepatotoxicity occur within the first 6 months of therapy and in patients with multiple risk factors for liver damage 2

Hematologic Toxicities

• Leukopenia was reported at a higher frequency compared to placebo in clinical trials 1
• Rare but serious reports of pancytopenia, agranulocytosis, and thrombocytopenia have been documented 2

Other Notable Toxicities

• Headache and dizziness are common adverse effects 2, 3
• Teratogenicity - contraindicated in pregnancy (Category X) 4
• Should not be used in nursing mothers 2

Monitoring Recommendations

• Baseline assessment: Complete history and physical examination, CBC with differential, liver function tests, and pregnancy test if indicated 2, 3
• Monthly CBC with differential and liver function tests for the first 6 months 2, 3
• After 6 months, continue monitoring every 6-8 weeks if stable 2, 3

Special Considerations

• Contraindicated in patients with hypersensitivity to leflunomide or its metabolites 2, 3
• Rifampin increases leflunomide levels and should be used with caution 2, 3

Leflunomide Side Effects and Monitoring

Gastrointestinal and Hematologic Side Effects

• Other GI effects include dyspepsia, abdominal pain, and loss of appetite, as reported by the American Academy of Dermatology, with an incidence of these effects occurring in patients taking leflunomide 5, 6
• Leukopenia occurs at a higher frequency compared to placebo, as noted by the American Academy of Dermatology, in patients receiving leflunomide 5, 6

Dermatologic Effects

• Rare serious skin reactions including Stevens-Johnson syndrome and DRESS syndrome have been reported, according to Arthritis and Rheumatology, in patients taking leflunomide 7