Lamisil (terbinafine hydrochloride) is a leading oral and topical antifungal medication indicated for the treatment of dermatophyte infections of the skin and nails. As a member of the allylamine class of antifungals, it works by inhibiting squalene epoxidase, a key enzyme in ergosterol synthesis, leading to fungal cell death. With over three decades of clinical use and extensive research supporting its efficacy, Lamisil remains a first-line therapeutic option for fungal infections. This comprehensive product card provides healthcare professionals with detailed prescribing information and clinical considerations.

Features

• Contains terbinafine hydrochloride as the active pharmaceutical ingredient
• Available in multiple formulations: 250 mg oral tablets, 1% topical cream, 1% topical solution, and 1% topical spray
• Exhibits fungicidal activity against dermatophytes including Trichophyton, Microsporum, and Epidermophyton species
• Demonstrated bioavailability of approximately 70-80% following oral administration
• Protein binding exceeds 99% in plasma, primarily to albumin and lipoproteins
• Hepatic metabolism via multiple CYP450 isoenzymes including CYP2C9, CYP1A2, CYP3A4, and CYP2C8

Benefits

• Achieves high clinical and mycological cure rates in onychomycosis and tinea infections
• Provides persistent antifungal activity in the nail plate for months following treatment completion
• Offers convenient once-daily dosing regimen for oral formulation
• Demonstrates superior efficacy compared to azole antifungals for dermatophyte infections
• Shows minimal drug interactions compared to azole antifungals
• Available in multiple formulations allowing for tailored treatment approaches

Common use

Lamisil is primarily prescribed for the treatment of dermatophytoses including onychomycosis of the toenails or fingernails caused by dermatophytes, tinea pedis (athlete’s foot), tinea cruris (jock itch), and tinea corporis (ringworm). The oral formulation is particularly effective for moderate to severe onychomycosis where topical therapy alone may be insufficient. Topical formulations are indicated for mild to moderate cutaneous fungal infections and may be used as adjunctive therapy with oral treatment.

Dosage and direction

Oral tablets: The standard adult dosage for onychomycosis is 250 mg once daily. Treatment duration is 6 weeks for fingernail infections and 12 weeks for toenail infections. Take with or without food, though consistent administration with food may improve gastrointestinal tolerance.

Topical formulations: Apply a thin layer to affected area once or twice daily, depending on formulation and infection severity. For cream and solution: cleanse and dry area thoroughly before application, covering affected area and approximately 1/2 inch of surrounding healthy skin. For spray: hold container upright 4-6 inches from affected area and spray until covered.

Continue treatment for the full prescribed duration even if symptoms improve earlier to prevent recurrence.

Precautions

Monitor liver function tests (ALT, AST) before initiating treatment and periodically during therapy, especially for treatments exceeding 6 weeks. Use with caution in patients with pre-existing liver disease or hepatic enzyme elevations. Monitor for symptoms of hepatotoxicity including nausea, vomiting, abdominal pain, or jaundice. Perform baseline and periodic visual exams as terbinafine has been associated with visual disturbances. Use caution in patients with renal impairment (creatinine clearance ≤50 mL/min); consider reduced dosage. May cause taste disturbance that usually resolves upon discontinuation but may persist in some cases.

Contraindications

Hypersensitivity to terbinafine, other allylamine antifungals, or any component of the formulation. Chronic or active liver disease. Severe renal impairment (creatinine clearance <50 mL/min). Not recommended during pregnancy (Category B) unless potential benefit justifies potential risk. Contraindicated in breastfeeding women due to secretion in breast milk.

Possible side effects

Common (≥1/100 to <1/10): Headache, gastrointestinal disturbances (diarrhea, dyspepsia, nausea, abdominal pain), rash, pruritus, urticaria, taste disturbance, elevated liver enzymes

Uncommon (≥1/1,000 to <1/100): Dizziness, visual disturbances, fatigue, malaise, arthralgia, myalgia

Rare (<1/1,000): Severe skin reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis), hepatobiliary dysfunction, hepatitis, cholestatic hepatitis, blood dyscrasias (neutropenia, agranulocytosis, thrombocytopenia), pancytopenia, lupus erythematosus, psoriasis exacerbation

Drug interaction

Terbinafine is a moderate inhibitor of CYP2D6. Use caution with coadministration of:

• CYP2D6 substrates: tricyclic antidepressants, selective serotonin reuptake inhibitors, beta-blockers, antiarrhythmics (flecainide, propafenone)
• Warfarin: may potentiate anticoagulant effect
• Rifampin: decreases terbinafine concentrations by 100%
• Cimetidine: increases terbinafine concentrations by 33%
• Cyclosporine: terbinafine may decrease cyclosporine concentrations
• Oral contraceptives: no significant interaction observed

Missed dose

If a dose is missed, take it as soon as remembered unless it is almost time for the next dose. Do not double the dose to make up for a missed dose. Resume regular dosing schedule. For topical formulations, apply as soon as remembered and continue with regular application schedule.

Overdose

Symptoms may include nausea, vomiting, abdominal pain, dizziness, rash, frequent urination, and headache. In cases of massive overdose, hepatic and renal toxicity may occur. There is no specific antidote. Treatment should be supportive and symptomatic. Gastric lavage may be considered if performed soon after ingestion. Activated charcoal may reduce drug absorption. Terbinafine is not dialyzable due to high protein binding.

Storage

Store at room temperature (15-30°C or 59-86°F). Protect from light and moisture. Keep container tightly closed. Do not freeze. Keep all medications out of reach of children and pets. Do not use after expiration date printed on packaging.

Disclaimer

This information is intended for healthcare professionals and should not replace professional medical advice, diagnosis, or treatment. Always consult appropriate prescribing information and clinical guidelines before initiating therapy. Dosage and administration may vary based on individual patient factors. The prescriber should be familiar with complete prescribing information including boxed warnings.

Reviews

Clinical studies demonstrate mycological cure rates of 70-85% and clinical cure rates of 60-75% for onychomycosis with oral terbinafine. Topical formulations show complete cure rates of 30-50% for cutaneous fungal infections. Multiple meta-analyses confirm terbinafine’s superiority over azole antifungals for dermatophyte infections. Long-term follow-up studies show sustained cure rates of 70-80% at 5 years for successfully treated onychomycosis. The medication is generally well-tolerated with most adverse effects being mild and transient.