Pharmacokinetics

In one study conducted in healthy subjects for 14 days, 6 grams of Mentax® Cream, 1%, was applied once daily to the dorsal skin (3,000 cm ² ) of 7 subjects, and 20 grams of the cream was applied once daily to the arms, trunk and groin areas (10,000 cm ² ) of another 12 subjects. After 14 days of topical applications, the 6-gram dose group yielded a mean peak plasma butenafine HCl concentration, Cmax, of 1.4 ± 0.8 ng/mL, occurring at a mean time to the peak plasma concentration, Tmax, of 15 ± 8 hours, and a mean area under the plasma concentration-time curve, AUC _{0-24 hrs} of 23.9 ± 11.3 ng-hr/mL. For the 20-gram dose group, the mean Cmax was 5.0 ± 2.0 ng/mL, occurring at a mean Tmax of 6 ± 6 hours, and the mean AUC _{0-24 hrs} was 87.8 ± 45.3 ng-hr/mL. A biphasic decline of plasma butenafine HCl concentrations was observed with the half-lives estimated to be 35 hours and > 150 hours, respectively. At 72 hours after the last dose application, the mean plasma concentrations decreased to 0.3 ± 0.2 ng/mL for the 6-gram dose group and 1.1 ± 0.9 ng/mL for the 20-gram dose group. Low levels of butenafine HCl remained in the plasma 7 days after the last dose application (mean: 0.1 ± 0.2 ng/mL for the 6-gram dose group, and 0.7 ± 0.5 ng/mL for the 20-gram dose group). The total amount (or % dose) of butenafine HCl absorbed through the skin into the systemic circulation has not been quantitated. It was determined that the primary metabolite in urine was formed through hydroxylation at the terminal t -butyl side-chain.

In 11 patients with tinea pedis, Mentax® Cream, 1%, was applied by the patients to cover the affected and immediately surrounding skin area once daily for 4 weeks, and a single blood sample was collected between 10 and 20 hours following dosing at 1, 2 and 4 weeks after treatment. The plasma butenafine HCl concentration ranged from undetectable to 0.3 ng/mL.

In 24 patients with tinea cruris, Mentax® Cream, 1 %, was applied by the patients to cover the affected and immediately surrounding skin area once daily for 2 weeks (mean average daily dose: 1.3 ± 0.2 g). A single blood sample was collected between 0.5 and 65 hours after the last dose, and the plasma butenafine HCl concentration ranged from undetectable to 2.52 ng/mL (mean ± SD: 0.91 ± 0.15 ng/mL). Four weeks after cessation of treatment, the plasma butenafine HCl concentration ranged from undetectable to 0.28 ng/mL.

Microbiology

Butenafine HCl has been shown to be active against most strains of the following microorganisms, both in vitro and in clinical infections as described in the INDICATIONS AND USAGE section:

Epidermophyton floccosum

Trichophyton mentagrophytes

Trichophyton rubrum

Trichophyton tonsurans

CLINICAL STUDIES

Interdigital Tinea Pedis

Once Daily Four Week Dosing

In the following data presentations, patients with interdigital tinea pedis in the absence of moccasin-type tinea pedis and onychomycosis were studied. The term "Mycological Cure" is defined as both negative KOH and culture. The term "Effective Treatment" refers to patients who had a "Mycological Cure" and an Investigator's Global of either "Excellent" (80% to 99% improvement) or "Cleared" (100% improvement). The term "Overall Cure" refers to patients who had both a "Mycological Cure" and an Investigator's Global Assessment of "Cleared" (100% improvement).

Data from the two controlled studies in which Mentax® Cream, 1%, was used once daily for 4 weeks have been combined in the table below. Patients were treated for 4 weeks and evaluated 4 weeks post-treatment. In the "per protocol" analysis shown in the table below, statistical significance (Mentax® vs. vehicle) was assessed 4 weeks post-treatment.

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