Short-duration topical treatment of tinea pedis using terbinafine emulsion gel: results of a dose-ranging clinical trial

Film-Forming Systems for the Delivery of DNDI-0690 to Treat Cutaneous Leishmaniasis

In cutaneous leishmaniasis (CL), parasites reside in the dermis, creating an opportunity for local drug administration potentially reducing adverse effects and improving treatment adherence compared to current therapies. Polymeric film-forming systems (FFSs) are directly applied to the skin and form a thin film as the solvent evaporates. In contrast to conventional topical dosage forms, FFSs strongly adhere to the skin, favouring sustained drug delivery to the affected site, reducing the need for frequent applications, and enhancing patient compliance. This study reports the first investigation of the use of film-forming systems for the delivery of DNDI-0690, a nitroimidazole compound with potent activity against CL-causing Leishmania species. A total of seven polymers with or without plasticiser were evaluated for drying time, stickiness, film-flexibility, and cosmetic attributes; three FFSs yielded a positive evaluation for all test parameters. The impact of each of these FFSs on the permeation of the model skin permeant hydrocortisone (hydrocortisone, 1% (w/v) across the Strat-M membrane was evaluated, and the formulations resulting in the highest and lowest permeation flux (Klucel LF with triethyl citrate and Eudragit RS with dibutyl sebacate, respectively) were selected as the FFS vehicle for DNDI-0690. The release and skin distribution of the drug upon application to Leishmania-infected and uninfected BALB/c mouse skin were examined using Franz diffusion cells followed by an evaluation of the efficacy of both DNDI-0690 FFSs (1% (w/v)) in an experimental CL model. Whereas the Eudragit film resulted in a higher permeation of DNDI-0690, the Klucel film was able to deposit four times more drug into the skin, where the parasite resides. Of the FFSs formulations, only the Eudragit system resulted in a reduced parasite load, but not reduced lesion size, when compared to the vehicle only control. Whereas drug delivery into the skin was successfully modulated using different FFS systems, the FFS systems selected were not effective for the topical application of DNDI-0690. The convenience and aesthetic of FFS systems alongside their ability to modulate drug delivery to and into the skin merit further investigation using other promising antileishmanial drugs.

Antifungal efficacy of atorvastatin-containing emulgel in the treatment of oral and vulvovaginal candidiasis

Drug repositioning has been an important ally in the search for new antifungal drugs. Statins are drugs that act to prevent sterol synthesis in both humans and fungi and for this reason they are promissory candidates to be repositioned to treat mycoses. In this study we evaluated the antifungal activity of atorvastatin by in vitro tests to determine the minimum inhibitory concentration against azole resistant Candida albicans and its mechanisms of action. Moreover, the efficacy of both atorvastatin-loaded oral and vaginal emulgels (0.75%, 1.5% and 3% w/w) was evaluated by means of in vivo experimental models of oral and vulvovaginal candidiasis, respectively. The results showed that atorvastatin minimal inhibitory concentration against C. albicans was 31.25 μg/ml. In oral candidiasis experiments, the group treated with oral emulgel containing 3.0% atorvastatin showcased total reduction in fungal load after nine days of treatment. Intravaginal delivery atorvastatin emulgel showed considerable effectiveness at the concentration of 3% (65% of fungal burden reduction) after nine days of treatment. From these findings, it is possible to assert that atorvastatin may be promising for drug repositioning towards the treatment of these opportunistic mycoses.

The potential of polymeric film-forming systems as sustained delivery platforms for topical drugs

INTRODUCTION

Dosing regimens requiring multiple daily applications frequently result in poor patient compliance, especially in the treatment of chronic skin diseases. Consequently, development of sustained delivery systems for topical drugs permitting less frequent dosing is of continuing interest for dermatological therapy.

AREAS COVERED

This potential of polymeric film-forming systems (FFS), created in situ on the skin, as sustained delivery platforms for topical drug delivery is reviewed. Key formulation parameters that determine delivery efficiency are considered focussing on those that permit a drug reservoir to be established in the upper layers of the skin and/or on the skin surface from which release can be sustained over a prolonged period. The advantageous and superior cosmetic attributes of FFS (compared to conventional semi-solid formulations) that offer significantly improved patient compliance are also addressed.

EXPERT OPINION

The promise of polymeric FFS as convenient and aesthetic platforms for sustained topical drug delivery is clear. Manipulation of the formulation allows the delivery profile to be customized and optimized to take advantage of both a rapid, initial input of drug into the skin (likely due to a transient period of supersaturation) and a slower, controlled release over an extended time from the residual film created thereafter.

Update on terbinafine with a focus on dermatophytoses

Since terbinafine was introduced on the world market 17 years ago, it has become the leading antifungal for the treatment of superficial fungal infections, aided by unique pharmacologic and microbiologic profiles. This article reviews mode of action, antimycotic spectrum and disposition profile of terbinafine. It examines the data, accumulated over 15 years, on the comparative efficacy of terbinafine (vs griseofulvin, itraconazole, fluconazole) in the management of the infections for which it is primarily indicated (eg, dermatophytoses) and provides a brief discussion on its use for the treatment of non-dermatophyte infections. Finally, the available data on the newest topical and systemic formulations are introduced.

[Topical terbinafine. Reduction of duration of therapy for tinea pedis]

Superficial fungal infections are common and worldwide in distribution. Latest estimates suggest one- third of the population in Europe has a fungal infection of their feet, with dermatophyte infections of the skin of the feet (tinea pedis) most common. Tinea pedis interdigitalis is by far most common and can be effectively treated topically. Common agents include azoles, hydroxypyridones and allylamines, with morpholines used less frequently. While most antifungals have mainly fungistatic effects on dermatophytes, the causative agents of tinea pedis, terbinafine--an allylamine--is fungicidal. Due to this feature shorter treatment periods are possible using topical terbinafine. For effective treatment of uncomplicated tinea pedis interdigitalis, azole cream preparations are often used twice daily for four weeks whereas 1% terbinafine cream can be applied once a day for one week. Since 2006, 1% terbinafine is also available as a film-forming solution (FFS), which makes single-dose treatment possible. FFS may prove superior in daily practice with increased compliance and thus reduced recurrences.

In vitro Skin Permeability of Different Terbinafine Hydrochloride Formulations

The objectives of the study are to determine the in vitro permeability of different terbinafine hydrochloride formulations through human skin and to measure the respective concentrations of each formulation within the exposed skin tissue. The permeation of three commercially available 1% terbinafine hydrochloride formulations and two terbinafine hydrochloride solutions of 10 and 20 mg/ml through human skin was investigated using an in vitro continuous flow-through perfusion system. The terbinafine hydrochloride retained in the skin was extracted and analysed. The terbinafine hydrochloride from the different formulations readily diffused into the skin tissue. However, no flux values for any of the terbinafine hydrochloride formulations through the skin into the receptor fluid were found. The mean terbinafine hydrochloride concentrations in the skin after 24 h exposure to the three commercial formulations were 3.589, 1.590 and 4.219 μg/ml respectively. The mean terbinafine hydrochloride concentrations in the skin after 24 h of exposure to the terbinafine hydrochloride solutions (PBS/Methanol 1:1) of 10 and 20 mg/ml were 85.280 and 154.680 μg/ml respectively. The mean terbinafine hydrochloride concentration in the skin exposed to the 10 mg/ml PBS/Methanol solution was higher than those from the three commercial formulations. Terbinafine seems to accumulate in skin/bind to the skin, rather than to diffuse through the skin into the receptor compartment. This unique pharmacokinetic property of terbinafine hydrochloride may enhance its efficacy as topical antifungal and reduce systemic side effects.