Leflunomide Viatris (Leflunomide)

Leflunomide is a disease‑modifying antirheumatic drug that targets inflammatory arthritis conditions.

• Rheumatoid arthritis: reduces joint inflammation, pain and slows structural damage.
• Psoriatic arthritis: improves skin lesions and joint symptoms.
• Moderate to severe active rheumatoid arthritis: helps achieve clinical remission when conventional therapy is insufficient.

• Leflunomide inhibits the mitochondrial enzyme dihydroorotate dehydrogenase, which blocks de novo pyrimidine synthesis. This limits the proliferation of activated lymphocytes, thereby reducing the autoimmune response that drives joint inflammation in rheumatoid and psoriatic arthritis.

Adverse reactions may range from mild to severe and should be monitored throughout therapy.

Common Side Effects

• Diarrhea: mild to moderate gastrointestinal upset.
• Nausea: occasional feeling of queasiness.
• Alopecia: reversible hair thinning.
• Rash: skin erythema or pruritus.
• Elevated liver enzymes: transient increase in ALT/AST.
• Hypertension: rise in blood pressure readings.

Serious or Rare Side Effects

• Severe liver injury: hepatitis or hepatic failure.
• Bone marrow suppression: neutropenia or anemia.
• Pulmonary toxicity: interstitial lung disease.
• Stevens‑Johnson syndrome: severe skin reaction.
• Serious infections: opportunistic bacterial or viral infections.
• Teratogenicity: fetal malformations if exposure occurs during pregnancy.

Before initiating therapy, clinicians should assess patient history and monitor laboratory parameters.

• Pregnancy contraindication: avoid use in pregnant women; teratogenic risk is category X.
• Liver function: obtain baseline tests and monitor periodically.
• Hematology: perform regular complete blood counts to detect cytopenias.
• Live vaccines: do not administer during treatment.
• Renal impairment: adjust dose cautiously in severe renal dysfunction.
• Store at ambient temperature: keep below 25 °C, in original packaging, protected from moisture.

Leflunomide may interact with several medicines, requiring careful management.

Major Interactions (Avoid)

• Warfarin: increased anticoagulant effect, risk of bleeding.
• Teriflunomide: additive toxicity, avoid concurrent use.
• Live vaccines: heightened risk of infection.
• Immunosuppressants (e.g., cyclosporine): amplified immunosuppression.
• Cholesterol‑binding resins (e.g., cholestyramine): reduce leflunomide absorption.

Moderate Interactions (Monitor Closely)

• Statins: possible increase in muscle toxicity.
• Antihypertensives: potential alteration of blood pressure control.
• Oral contraceptives: reduced efficacy, advise additional contraception.
• Methotrexate: additive hepatic toxicity.
• Azathioprine: enhanced bone‑marrow suppression.