Leflunomide Medac (Leflunomide)

Leflunomide is a disease‑modifying antirheumatic drug that targets inflammatory pathways in autoimmune joint disease.

• Rheumatoid arthritis: reduces joint inflammation and slows structural damage.
• Psoriatic arthritis: improves skin lesions and joint symptoms.
• Active adult disease: helps control overall disease activity and functional impairment.

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

Leflunomide may cause a range of adverse reactions, from mild to severe.

Common Side Effects

• Diarrhoea: loose stools, often mild to moderate.
• Nausea: feeling of sickness, may be transient.
• Alopecia: thinning or loss of hair.
• Rash: skin redness or itching.
• Elevated liver enzymes: mild transaminase rise.
• Hypertension: increased blood pressure readings.

Serious or Rare Side Effects

• Severe liver injury: jaundice, hepatic failure.
• Stevens‑Johnson syndrome: severe skin blistering.
• Bone marrow suppression: low blood counts, risk of infection.
• Interstitial lung disease: breathing difficulty, cough.
• Severe infections: opportunistic bacterial or viral infections.
• Teratogenicity: risk of fetal malformations if exposure occurs during pregnancy.

Before initiating therapy, clinicians should evaluate baseline health and monitor patients regularly.

• Liver monitoring: check transaminases before start and periodically thereafter.
• Blood pressure: measure regularly and manage hypertension if present.
• Pregnancy avoidance: contraindicated in pregnancy; effective contraception required.
• Infection risk: assess for active infections and vaccinate appropriately.
• Discontinue if serious adverse events occur: stop therapy and provide supportive care.
• Store at room temperature: keep in the original container, protect from moisture and direct sunlight.

Leflunomide can alter the activity of several concomitant medicines; careful review is essential.

Major Interactions (Avoid)

• Warfarin: increased anticoagulant effect, may cause bleeding.
• Methotrexate: additive hepatotoxicity, heightened liver risk.
• Bupropion: increased plasma levels, risk of seizures.

Moderate Interactions (Monitor Closely)

• Statins: potential for increased muscle toxicity.
• Azathioprine: combined immunosuppression, monitor blood counts.
• Live vaccines: reduced efficacy, consider timing or avoidance.