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Terbinafine hydrochloride
Terbinafine hydrochloride (Lamisil)
Terbinafine hydrochloride
(ter-BIN-ah-feen)
Pregnancy Category: B Lamisil (Rx) (OTC)

Classification: Antifungal agent

Action/Kinetics: Inhibits squalene epoxidase, a key enzyme in the sterol biosynthesis in fungi. Results in ergosterol deficiency and a corresponding accumulation of squalene leading to fungal cell death. Approximately 75% of cutaneously absorbed drug is excreted in the urine, mostly as metabolites. Well absorbed following PO administration, with first-pass metabolism being about 40%. Peak plasma levels: 1 mcg/mL within 2 hr. Food enhances absorption. Over 99% bound to plasma proteins. Slowly excreted from adipose tissue and skin. Extensively metabolized with about 70% of the dose eliminated in the urine. Renal or hepatic disease decreases clearance from the body.

Uses: Topical use: Interdigital tinea pedis (athletes' foot), tinea cruris (jock itch), or tinea corporis (ringworm) due to Epidermophyton floccosum, Trichophyton mentagrophytes or T. rubrum. Plantar tinea pedis. Tinea versicolor due to Malassezia furfur. Investigational: Cutaneous candidiasis and tinea versicolor.Oral use: Onychomycosis of the toenail or fingernail due to dermatophytes.

Contraindications: Ophthalmic or intravaginal use. PO use in preexisting liver disease or renal impairment (C_CR less than 50 mL/min). Lactation.

Special Concerns: Safety and efficacy have not been determined in children less than 12 years of age.

Side Effects: Following topical use. Dermatologic: Irritation, burning, itching, dryness.
Following oral use. GI: Diarrhea, dyspepsia, abdominal pain, nausea, flatulence. Dermatologic: Rash, pruritus, urticaria. Other: Headache, taste or visual disturbances. Rarely, symptomatic idiosyncratic hepatobiliary dysfunction (including cholestatic hepatitis), serious skin reactions, severe neutropenia, allergic reactions (including anaphylaxis).

Laboratory Test Alterations: Liver enzyme abnormalities that are two or more times the upper limit of the normal range. Absolute neutrophil counts.

Drug Interactions: Cimetidine / Terbinafine clearance is by one-third Cyclosporine / Cyclosporine clearance Rifampin / Terbinafine clearance (100%)

How Supplied: Cream: 1%; Spray: 1%; Tablet: 250 mg

Dosage
•Cream Interdigital tinea pedis.
Apply to cover the affected and immediately surrounding areas b.i.d. for 1 week. The cream is otc.
Tinea cruris or tinea corporis.
Apply to cover the affected and immediately surrounding areas 1-2 times/day for 1 week.
•Spray Tinea pedis, Tinea versicolor.
Spray b.i.d. for one week.
Tinea corporis, Tinea cruris.
Spray once daily for one week.
•Tablets Onychomycosis.
250 mg/day for 6 weeks if fingernails are affected and 250 mg/day for 12 weeks if toenails are affected. Alternatively, intermittent dosing may be used: 500 mg daily for 1 week each month (use 2 months for fingernails and 4 months for toenails). The optimal clinical effect is observed several months after mycologic cure and cessation of treatment due to slow period for outgrowth of healthy nails.