Lamisil (terbinafine hydrochloride) is a leading oral and topical antifungal medication indicated for the treatment of dermatophyte infections. As a member of the allylamine class, it functions by inhibiting squalene epoxidase, a key enzyme in ergosterol synthesis, resulting in fungicidal activity against susceptible organisms. Its efficacy is well-established through extensive clinical trials, making it a first-line choice among healthcare providers for fungal nail infections (onychomycosis) and tinea corporis, cruris, and pedis. Available in tablet, cream, and spray formulations, Lamisil offers targeted therapy with a well-characterized safety profile when used as directed.

Features

• Contains terbinafine hydrochloride as the active ingredient
• Available in 250 mg oral tablets and 1% topical formulations (cream, spray, solution)
• Exhibits broad-spectrum activity against dermatophytes such as Trichophyton species
• Fungicidal mechanism of action via inhibition of ergosterol biosynthesis
• Requires prescription for oral formulation; some topical forms available over-the-counter
• Manufactured under strict pharmaceutical quality control standards

Benefits

• Achieves high mycological cure rates in onychomycosis and superficial skin infections
• Promotes healthy nail regrowth by eradicating the underlying fungal infection
• Reduces symptoms such as pruritus, scaling, and inflammation associated with tinea infections
• Offers convenient once-daily dosing for oral administration
• Provides localized treatment option with minimal systemic exposure through topical formulations
• Supported by decades of clinical use and post-marketing surveillance data

Common use

Lamisil is primarily prescribed for the treatment of onychomycosis of the toenail or fingernail due to dermatophytes. It is also indicated for tinea corporis (ringworm), tinea cruris (jock itch), and tinea pedis (athlete’s foot). Topical formulations are typically used for superficial skin infections, while oral therapy is reserved for more extensive involvement or nail infections where topical penetration is insufficient. Diagnosis should be confirmed by potassium hydroxide (KOH) preparation or fungal culture prior to initiating treatment.

Dosage and direction

Oral tablets:

• Adults: 250 mg once daily
• Fingernail onychomycosis: 6 weeks duration
• Toenail onychomycosis: 12 weeks duration

Topical formulations:

• Apply thin layer to affected area and surrounding skin once or twice daily
• Duration typically ranges from 1 week (tinea corporis/cruris) to 4 weeks (tinea pedis)
• Wash hands before and after application unless treating hands

Take oral tablets with or without food. For optimal absorption, avoid consuming aluminum-containing antacids within 2 hours of administration. Complete the full course of therapy even if symptoms improve earlier to prevent recurrence.

Precautions

• Monitor liver function tests (ALT, AST) before initiating oral therapy and periodically during treatment
• Assess for pre-existing liver disease or alcohol abuse; contraindicated in chronic or active liver disease
• Use with caution in patients with renal impairment (creatinine clearance ≤50 mL/min)
• May cause taste disturbance (dysgeusia) which usually resolves upon discontinuation
• Topical formulations: For external use only; avoid contact with eyes, nose, mouth, and other mucous membranes
• Discontinue use and consult healthcare provider if irritation or hypersensitivity develops

Contraindications

• Hypersensitivity to terbinafine, any allylamine antifungal, or other formulation components
• Chronic or active liver disease
• Severe renal impairment (creatinine clearance <50 mL/min)
• History of drug-induced liver injury from terbinafine
• Pregnancy and breastfeeding (for oral formulation)
• Concurrent use with specific CYP2D6 substrates with narrow therapeutic index

Possible side effect

Common (≥1/100):

• Headache
• Gastrointestinal disturbances (nausea, diarrhea, abdominal pain)
• Rash and pruritus
• Taste disturbance (dysgeusia)
• Topical: Application site reactions (burning, irritation, dryness)

Serious (<1/1000):

• Hepatobiliary dysfunction (elevated liver enzymes, hepatitis, liver failure)
• Severe cutaneous adverse reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis)
• Hematological effects (neutropenia, agranulocytosis, thrombocytopenia)
• Lupus erythematosus and lupus-like reactions
• Visual disturbances and changes in ocular lens and retina
• Depression and anxiety symptoms

Drug interaction

• CYP2D6 substrates: May increase concentrations of dextromethorphan, metoprolol, imipramine
• Rifampin: Reduces terbinafine plasma concentrations by 40%
• Cimetidine: Increases terbinafine plasma concentrations by 33%
• SSRIs (fluoxetine, paroxetine): Potential pharmacokinetic interaction
• Oral contraceptives: No clinically significant interaction observed
• Warfarin: Monitor prothrombin time due to potential potentiation

Missed dose

Take the missed dose as soon as remembered unless it is nearly time for the next scheduled dose. Do not double the dose to make up for the missed one. Resume the regular dosing schedule. For topical formulations, apply the missed dose when remembered unless close to next application time.

Overdose

Oral overdose: May manifest as nausea, vomiting, abdominal pain, dizziness, rash, and urinary retention. There is no specific antidote. Employ supportive measures including gastric lavage (if presented early) and activated charcoal. Monitor hepatic and renal function. Hemodialysis is unlikely to be effective due to high protein binding.

Topical overdose: Unlikely to cause systemic effects due to limited absorption. Wash affected area with soap and water if accidental ingestion or extensive application occurs.

Storage

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

Disclaimer

This information is for educational purposes only and does not constitute medical advice. Consult a qualified healthcare professional for diagnosis and treatment recommendations. Do not initiate or discontinue medication without medical supervision. Individual results may vary based on clinical presentation, adherence, and underlying health conditions.

Reviews

“After struggling with persistent onychomycosis for years, a 12-week course of oral Lamisil resulted in complete clearance. Monitoring liver enzymes monthly was straightforward through my primary care provider.” — Verified patient, 54

“As a dermatologist, I prescribe terbinafine first-line for confirmed dermatophyte onychomycosis. The cure rates are superior to azoles, and the safety profile is well-established with appropriate monitoring.” — Board-certified dermatologist, 15 years experience

“Topical Lamisil spray resolved my tinea pedis within two weeks where other OTC options had failed. No irritation noted, and the spray application was convenient for foot use.” — Verified user, 38