Lamisil (Terbinafine Hydrochloride)

Lamisil (terbinafine) is an allylamine antifungal used to treat superficial dermatophyte infections of the skin.

• Tinea pedis: reduces fungal growth and relieves itching, scaling and redness on the feet.
• Tinea corporis: clears ring‑shaped lesions and eliminates the causative dermatophytes on the body.
• Tinea cruris: improves groin area symptoms by eradicating the infection and decreasing inflammation.
• Dermatophyte skin infections: provides broad‑spectrum activity against Trichophyton, Microsporum and Epidermophyton species, promoting lesion resolution.

• Terbinafine inhibits the fungal enzyme squalene epoxidase, a key step in ergosterol synthesis. By blocking this pathway, intracellular squalene accumulates while ergosterol levels fall, disrupting the structure and function of the fungal cell membrane. The resulting membrane instability leads to fungal cell death, providing a fungicidal effect against dermatophytes. The inhibition is selective for fungal cells, sparing human cholesterol pathways, and the drug penetrates the stratum corneum to reach the infection site.

Topical terbinafine may cause local skin reactions, ranging from mild irritation to rare severe hypersensitivity.

Common Side Effects

• Itching: mild pruritus at the application site.
• Redness: localized erythema.
• Burning sensation: transient heat feeling.
• Scaling: flaking of treated skin.
• Dryness: reduced skin moisture.
• Irritation: mild discomfort or stinging.

Serious or Rare Side Effects

• Allergic reaction: hives, swelling, or difficulty breathing.
• Severe skin rash: widespread erythema or bullous lesions.
• Contact dermatitis: intense inflammation and blistering.
• Angioedema: rapid swelling of face, lips or tongue.
• Systemic toxicity: rare liver enzyme elevation with extensive use.
• Anaphylaxis: life‑threatening hypersensitivity requiring emergency care.

Before using Lamisil topical, consider the following safety measures to minimize risks and ensure appropriate use.

• Assess hypersensitivity: confirm no known allergy to terbinafine or formulation components.
• Avoid broken skin: do not apply on open wounds, burns or ulcerated areas.
• Limit duration: follow prescriber’s recommended treatment length to reduce irritation risk.
• Monitor liver function: consider baseline assessment if extensive or prolonged use is anticipated.
• Do not apply to mucous membranes: keep away from eyes, mouth and genital mucosa.
• Store at room temperature: keep in original packaging, protect from moisture and direct sunlight.

Terbinafine topical has limited systemic absorption, yet certain drug combinations may require attention.

Major Interactions (Avoid)

• Concurrent oral terbinafine: combined use can increase systemic exposure and risk of toxicity.
• Strong CYP2D6 inhibitors: may affect metabolism of oral terbinafine, leading to elevated plasma levels.

Moderate Interactions (Monitor Closely)

• Other topical antifungals: simultaneous use may increase local irritation.
• Systemic azoles (e.g., itraconazole): may compete for metabolic pathways, warranting monitoring.
• Corticosteroid creams: may mask signs of infection or alter terbinafine efficacy.