Detection and Relevance of Naftifine Hydrochloride in the Stratum Corneum Up to Four Weeks Following the Last Application of Naftifine Cream and Gel, 2%

September 2013 | Volume 12 | Issue 9 | Original Article | 1004 | Copyright © September 2013


Stefan Plaum MD, Amit Verma DrPH MPH, Alan B. Fleischer Jr. MD,
Babajide Olayinka MSc, and Bhushan Hardas MD

Merz Pharmaceuticals, LLC, Greensboro, NC

Abstract
BACKGROUND: Two-week treatment using naftifine cream or gel, 2% has been shown to be efficacious in subjects with Tinea pedis and/or Tinea cruris, and in most cases, continued improvement has been observed following cessation of treatment for up to four weeks. One possible explanation for continuous post-treatment improvement is drug-levels remaining in the stratum corneum (SC) as a function of time.
OBJECTIVE: The objective is to use tape stripping methodology to assess the amount of drug available in the SC over a 28 day period following the last dose.
METHODS: This was an open-label, single-exposure study on subjects comparing the amount of drug that was absorbed into the SC following topical application for 2-weeks. Twelve subjects were dosed daily (6 with naftifine cream, 2% and 6 with naftifine gel, 2%). Subjects had twelve 8 cm2 test application sites demarcated on the upper back. Twenty-five individual sequential strips were obtained from each test site. Of these, 11 sites were dosed once daily with the drug (5.0μL/cm2) for days 1 to 14 and the final site served as the control. On days 15, 29, and 43, a site was stripped to collect the SC in order to process the amount of drug present.
RESULTS: Naftifine was present on all tape strip samples collected over the 28 day period following two weeks of application. Furthermore, the most relevant, deeper tape strip sets reflecting the SC, showed potentially clinically relevant presence of naftifine in the skin for 28-days post-treatment.
CONCLUSIONS: Naftifine was present in the tape strips on all sample collection days up to and including four weeks following the last drug application. These findings help explain the progressive improvement in clinical and mycological response rates during the treatment period and for up to four weeks post-treatment in the clinical trials using naftifine.

J Drugs Dermatol. 2013;12(9):1004-1008.

INTRODUCTION

Fungal infections in humans occur globally due to dermatophytes, yeasts, and molds and results from contact with infected humans, animals, soils, and fomites. They can be classified into three broad groups: superficial, subcutaneous, and systemic. Most superficial fungal infections of keratinized tissues such as the skin, nails, and hair are caused by dermatophytes that spread through contact with infected person or by self infection through transfer from another body part.1, 2
Dermatophytic infections, in general, are common in the US population, with up to 1 in 5 individuals infected at any one time.3, 4, 5 The majority of superficial fungal infections in the US are tinea infections, which are primarily caused by three types of dermatophytes: Trichophyton rubrum, Trichophyton mentagrophytes, and Epidermophyton floccosum.6 The most common tinea infections are tinea pedis, tinea cruris, and tinea corporis.
Tinea pedis, an infection of the foot, affects nearly 26.5 million people a year with half expected to suffer from reoccurring outbreaks,7 and is second only to acne for being a leading cause of skin infections in the US.8 Trichophyton rubrum has been found to be the leading cause of tinea pedis infection, accounting for two-thirds of all cases.8 Tinea cruris is a superficial fungal infection of the groin and surrounding tissue and is the second leading disease state for a tinea infection.9 Trichophyton rubrum and Trichophyton mentagrophytes have been isolated as the primary cause of tinea cruris; however, Epidermophyton floccosum is also a causative organism.9 As with tinea pedis infections, Trichophyton rubrum has been found to be the leading cause of tinea cruris infection, accounting for about three-fourths of all cases.2
Although oral medications can be used for the treatment of superficial fungal infections, topical medications have become a popular and effective treatment alternative due to the decreased risk of undesirable systemic effects. A common topical intervention is naftifine hydrochloride (HCl), a broad-spectrum topical antifungal drug in the allylamine class. Among the classes of topical treatments, allylamines have been shown to demonstrate better efficacy rates and shorter treatment courses than the azoles.10, 11, 12 Naftifine HCl displays potent fungicidal and fungistatic activity and clinically significant anti-inflammatory and anti-bacterial effects.13-16
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