Lamisil (Terbinafine Hydrochloride)

• Lamisil (terbinafine) is indicated for fungal skin and nail infections caused by dermatophytes and related organisms.
• Onychomycosis: eliminates the dermatophyte infection of the nail plate and matrix, leading to gradual restoration of normal nail appearance.
• Tinea pedis: treats athlete's foot by eradicating the causative fungus, reducing scaling, itching and redness on the feet.
• Tinea corporis: resolves ringworm lesions on the body, decreasing erythema, scaling and preventing further spread.
• Tinea cruris: clears jock itch infection in the groin area, relieving intense itching, redness and maceration.

• Terbinafine inhibits the fungal enzyme squalene epoxidase, a key step in ergosterol biosynthesis. By blocking this enzyme, the drug causes accumulation of squalene, which is toxic to fungal cells, and depletes ergosterol, an essential component of the fungal cell membrane. The resulting disruption of membrane integrity leads to fungal cell death, providing a fungicidal effect against dermatophytes, yeasts and some molds.

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

Common Side Effects

• Taste disturbance: altered taste or loss of taste.
• Gastrointestinal upset: nausea, abdominal discomfort or diarrhea.
• Headache: mild to moderate headache.
• Skin rash: mild erythematous rash.
• Elevated liver enzymes: transient increase in hepatic transaminases.

Serious or Rare Side Effects

• Severe hepatic injury: hepatitis, jaundice or liver failure.
• Stevens‑Johnson syndrome: life‑threatening skin detachment and mucosal involvement.
• Eosinophilic pneumonia: respiratory symptoms with eosinophil accumulation in lungs.
• Anaphylaxis: acute allergic reaction with airway compromise.
• Blood dyscrasias: agranulocytosis or pancytopenia.

Before prescribing terbinafine, clinicians should consider several safety precautions to minimize risk.

• Liver function monitoring: assess baseline transaminases and repeat if symptoms of hepatitis appear.
• Renal impairment: adjust dose or avoid in severe renal dysfunction.
• Hypersensitivity: discontinue immediately if rash, pruritus or systemic allergic reactions develop.
• Pregnancy and lactation: use only if benefit outweighs potential risk; category B.
• Drug interactions: review concomitant medications that affect CYP2D6 metabolism.
• Store at ambient temperature: keep below 25 °C in original packaging, protect from moisture.

Terbinafine interacts with several medicines; awareness of the interaction level guides clinical management.

Major Interactions (Avoid)

• Strong CYP2D6 inhibitors (e.g., fluoxetine, paroxetine, quinidine): may increase terbinafine plasma concentrations and risk of toxicity.
• Concurrent use with itraconazole or ketoconazole: additive hepatotoxicity risk.

Moderate Interactions (Monitor Closely)

• Warfarin: terbinafine may enhance anticoagulant effect, requiring INR monitoring.
• Oral contraceptives: efficacy may be reduced, consider alternative contraception.
• Sulfonylurea antidiabetics: possible increased hypoglycemia, monitor blood glucose.