Leflon (Leflunomide)

Leflunomide, the active component of Leflon, is employed in disease‑modifying strategies for inflammatory arthritis conditions.

• Rheumatoid arthritis: reduces joint inflammation, pain, and structural damage, improving functional ability.
• Psoriatic arthritis: alleviates skin lesions and joint symptoms, slowing disease progression.

• Leflunomide exerts its immunomodulatory effect by selectively inhibiting the mitochondrial enzyme dihydroorotate dehydrogenase (DHODH). This blockade impairs de novo synthesis of pyrimidine nucleotides, which are essential for the proliferation of activated T‑lymphocytes and other immune cells. The resulting reduction in lymphocyte expansion dampens the autoimmune response that drives chronic inflammation in rheumatoid and psoriatic arthritis. By limiting nucleotide availability, leflunomide also affects B‑cell activity and cytokine production, contributing further to its therapeutic effect.

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

Common Side Effects

• Nausea: mild to moderate stomach upset.
• Diarrhea: loose stools, may be transient.
• Alopecia: thinning or loss of hair.
• Rash: skin redness or itching.
• Headache: mild to moderate pain.
• Hypertension: increase in blood pressure.

Serious or Rare Side Effects

• Hepatotoxicity: elevated liver enzymes or liver failure.
• Severe infections: increased risk of bacterial, viral or fungal infections.
• Bone marrow suppression: anemia, leukopenia, or thrombocytopenia.
• Interstitial lung disease: inflammation and scarring of lung tissue.
• Stevens‑Johnson syndrome: severe skin and mucous membrane reaction.
• Vasculitis: inflammation of blood vessels, may cause organ damage.

When prescribing Leflon, clinicians should observe several safety precautions to minimize risk.

• Pregnancy contraindication: avoid use in pregnant women and ensure effective contraception during treatment and for a defined period after discontinuation.
• Liver monitoring: obtain baseline liver function tests and repeat regularly during therapy.
• Hematologic monitoring: perform complete blood count assessments before initiation and periodically thereafter.
• Renal impairment: use with caution in patients with reduced kidney function and adjust dose if necessary.
• Drug interactions: review concomitant medications for potential major interactions, especially anticoagulants and CYP1A2 inhibitors.
• Store at ambient temperature: keep below 25 °C, retain in original packaging, and protect from moisture.

Leflon can interact with other medicines, requiring attention to avoid reduced efficacy or increased toxicity.

Major Interactions (Avoid)

• Warfarin: increased anticoagulant effect leading to bleeding risk.
• Potent CYP1A2 inhibitors (e.g., fluvoxamine): raise leflunomide plasma levels, heightening toxicity.
• Live vaccines: risk of uncontrolled infection due to immunosuppression.
• Methotrexate: combined use may exacerbate hepatotoxicity and bone marrow suppression.
• Teriflunomide (if used): additive immunosuppressive effects.

Moderate Interactions (Monitor Closely)

• Azathioprine: may increase risk of bone marrow suppression.
• Cyclosporine: potential for enhanced nephrotoxicity.
• Statins: possible increase in muscle toxicity.
• Antihypertensives: leflunomide may elevate blood pressure, requiring dose adjustment.
• Oral contraceptives: reduced effectiveness, consider alternative contraception.