Lamisil (Terbinafine)

Lamisil (terbinafine) is used to treat fungal infections of the skin and nails.

• Onychomycosis: eradicates dermatophyte infection of the toenail or fingernail, improving nail appearance and preventing spread.
• Tinea pedis: relieves athlete’s foot symptoms by eliminating the causative fungi on the feet.
• Tinea corporis: clears ringworm lesions on the body by targeting the fungal organisms.
• Tinea cruris: treats jock itch by resolving fungal overgrowth in the groin area.
• Tinea capitis: combats scalp fungal infection, promoting hair regrowth and reducing inflammation.

• Terbinafine exerts its antifungal activity by inhibiting the enzyme squalene epoxidase, a key step in the ergosterol biosynthesis pathway of fungi. Blockade of this enzyme leads to accumulation of squalene, which is toxic to fungal cells, and a depletion of ergosterol, an essential component of the fungal cell membrane, resulting in cell death. The selective inhibition spares human cells because the target pathway is absent in mammals.

Terbinafine may cause adverse reactions, which are categorized by frequency and severity.

Common Side Effects

• Gastrointestinal discomfort: nausea, abdominal pain or dyspepsia.
• Headache: mild to moderate intensity.
• Skin rash: pruritic or erythematous eruptions.
• Taste disturbance: altered taste perception or loss of taste.

Serious or Rare Side Effects

• Hepatotoxicity: elevated liver enzymes or hepatitis.
• Severe cutaneous reactions: Stevens‑Johnson syndrome or toxic epidermal necrolysis.
• Hematologic abnormalities: neutropenia, thrombocytopenia or anemia.

Before prescribing terbinafine, clinicians should consider several safety precautions.

• Assess liver function: obtain baseline hepatic enzymes and monitor periodically.
• Evaluate hypersensitivity: avoid use in patients with known allergy to terbinafine or related compounds.
• Monitor renal function: adjust therapy in severe renal impairment.
• Review concomitant medications: consider potential drug interactions that may affect terbinafine levels.
• Counsel women of childbearing potential: pregnancy safety is not established; discuss risks.
• Store at room temperature: keep in the original packaging, protect from moisture and direct sunlight.

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

Major Interactions (Avoid)

• Rifampin: strong enzyme inducer that may markedly reduce terbinafine plasma concentrations.
• Ketoconazole: potent CYP inhibitor that can increase terbinafine exposure and risk of toxicity.
• Cimetidine: may raise terbinafine levels by inhibiting hepatic metabolism.

Moderate Interactions (Monitor Closely)

• Warfarin: terbinafine can enhance anticoagulant effect; monitor INR.
• Oral contraceptives: possible reduction in efficacy; advise additional contraceptive measures.
• Cyclosporine: increased risk of liver enzyme elevation; monitor hepatic function.