Lamisil (Terbinafine)

• Lamisil is an allylamine antifungal indicated for several dermatophyte infections.
• Onychomycosis: eradicates fungal infection of the toenails and fingernails, improving nail appearance and preventing spread.
• Tinea pedis: relieves athlete's foot symptoms and clears the infection of the feet.
• Tinea corporis: treats ringworm of the body, reducing redness and scaling.
• Tinea cruris: resolves jock itch caused by dermatophytes, alleviating itching and inflammation.

• Terbinafine inhibits the fungal enzyme squalene epoxidase, a key step in ergosterol biosynthesis. By blocking this pathway, intracellular squalene accumulates while ergosterol levels fall, disrupting fungal cell membrane integrity and leading to cell death. The selective inhibition targets fungal cells with minimal effect on human cholesterol synthesis.

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

Common Side Effects

• Gastrointestinal discomfort such as nausea, abdominal pain or diarrhoea.
• Headache or dizziness.
• Skin rash or pruritus.
• Altered taste sensation (dysgeusia).
• Elevated liver enzymes detected on routine testing.
• Mild fatigue.

Serious or Rare Side Effects

• Severe liver injury or hepatitis.
• Stevens‑Johnson syndrome or toxic epidermal necrolysis.
• Blood dyscrasias including neutropenia or agranulocytosis.
• Anaphylactic reactions.
• Severe skin reactions such as drug reaction with eosinophilia and systemic symptoms (DRESS).

• Before initiating therapy, clinicians should consider several safety measures.
• Assess liver function: obtain baseline hepatic enzymes and monitor periodically.
• Monitor for skin reactions: advise patients to report rash, blistering or mucosal involvement promptly.
• Review concomitant medications: check for drugs that share metabolic pathways.
• Use caution in pregnancy: category B, weigh benefits against potential risks.
• Avoid in patients with known hypersensitivity to terbinafine or other allylamines.
• Store below 25°C: keep in the original pack, protect from moisture.

Terbinafine can interact with other medicines through shared metabolic pathways.

Major Interactions (Avoid)

• Cimetidine: may increase terbinafine plasma levels, risking toxicity.
• Itraconazole: combined use can lead to elevated hepatic burden.
• Ritonavir (and other strong CYP3A4 inhibitors): may markedly raise terbinafine concentrations.

Moderate Interactions (Monitor Closely)

• Warfarin: monitor INR as terbinafine may enhance anticoagulant effect.
• Oral contraceptives: efficacy may be reduced; advise alternative contraception.
• Statins metabolised by CYP3A4 (e.g., simvastatin): monitor for myopathy.
• Antidepressants (e.g., fluoxetine): observe for increased side‑effect profile.