Lamisil (Terbinafine Hydrochloride)

Lamisil (terbinafine) is used to treat fungal infections caused by dermatophytes affecting skin and nails.

• Onychomycosis: eradicates the fungal infection of the toenail or fingernail, promoting normal nail growth.
• Tinea pedis (athlete’s foot): clears the fungal infection of the foot skin, relieving itching and scaling.
• Tinea corporis (ringworm): eliminates the dermatophyte infection of the body skin, restoring healthy appearance.

• Terbinafine inhibits fungal squalene epoxidase, a key enzyme in ergosterol synthesis. This inhibition leads to accumulation of squalene and depletion of ergosterol, disrupting the fungal cell membrane structure and causing cell death. The selective action targets dermatophyte organisms while sparing human cells, providing effective systemic antifungal therapy.

Terbinafine is generally well tolerated, but adverse reactions can occur.

Common Side Effects

• Gastrointestinal upset: nausea, abdominal discomfort or diarrhea.
• Headache: mild to moderate intensity.
• Altered taste sensation: temporary dysgeusia or loss of taste.
• Skin rash: mild erythema or pruritus.
• Elevated liver enzymes: mild, transient increases in hepatic transaminases.

Serious or Rare Side Effects

• Hepatotoxicity: signs of liver injury such as jaundice or dark urine.
• Severe cutaneous reactions: Stevens‑Johnson syndrome or toxic epidermal necrolysis.
• Hematologic abnormalities: neutropenia or eosinophilia.
• Peripheral neuropathy: numbness or tingling in extremities.
• Anaphylaxis: rare systemic allergic response.

Before initiating therapy, consider the following precautions.

• Assess liver function: obtain baseline hepatic enzymes and monitor periodically.
• Review medication history: avoid concomitant use with strong CYP inducers or inhibitors.
• Evaluate renal status: dose adjustment may be needed in severe impairment.
• Monitor for skin reactions: discontinue if severe rash or hypersensitivity develops.
• Counsel on alcohol use: limit intake as it may increase hepatic risk.
• Store at ambient temperature: keep below 25 °C, retain in original packaging, and protect from moisture.

Terbinafine may interact with other medicines; awareness of interaction severity is essential.

Major Interactions (Avoid)

• Strong CYP2D6 inhibitors (e.g., fluoxetine, paroxetine): can raise terbinafine plasma levels.
• CYP3A4 inducers (e.g., rifampin, carbamazepine): may markedly reduce terbinafine efficacy.

Moderate Interactions (Monitor Closely)

• Cimetidine: may increase terbinafine concentrations.
• Warfarin: potential for altered anticoagulant effect; monitor INR.
• Antiretrovirals metabolized by CYP enzymes: adjust therapy based on clinical response.
• Oral contraceptives: rare reports of reduced effectiveness; advise additional contraceptive measures.