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.