Superficial fungal infections are among the world's most common diseases. They are widely prevalent in India, especially during the prolonged summer months.

Till the 1940s, standard topical antifungal therapy was limited to Whitfield's ointment, Castellani's paint, and gentian violet. The explosive increase in fungal infections and widespread treatment failures during World War II led to a more aggressive search for better therapeutic measures. Today there are multiple modern topical antimycotics capable of eradicating human dermatomycoses.

Topical antifungals are generally considered as first line therapy for uncomplicated, superficial and relatively localised dermatomycoses due to their high efficacy and low potential for systemic adverse effects. The most commonly employed topical antifungals belong to three main classes: the polyenes, the azoles, and the allylamines/benzylamines. Other topical antimycotics (outside the three major classes) include ciclopirox olamine, selenium sulfide, and tolnaftate.

Butenafine hydrochloride is the only benzylamine class antifungal agent with a structure and mode of action similar to allylamines.

Butenafine acts by inhibiting the epoxidation of squalene, thus blocking the biosynthesis of ergosterol, an essential component of the fungal cell membrane. With the inhibition of squalene epoxidase, there is also an accumulation of intracellular squalene leading to disruption of the fungal cell membrane and death of the fungus.

Butenafine was approved for topical use in Japan in 1992. It has been the treatment of choice for tinea pedis, tinea corporis, tinea cruris, tinea versicolor, and cutaneous candidial infections. It was approved for topical use in the United States in 1997 and has been recently introduced in India.

Butenafine demonstrates fungicidal activity in vitro and in animal models against dermatophytes, candida albicans, aspergillus and other dimorphic fungi, including Sporothrix schenckii. Butenafine has been found in high concentrations (250 to 500mcg/gm of skin) in epidermis after topical application and small amounts are also found in the dermis, showing deeper penetration and prolonged cutaneous retention. This is as a result of its keratinophilic and lipophilic properties.

Clinical studies have shown that a once-daily application of butenafine for two weeks produces significant clinical improvement and mycologic cure rates ( 81% and 88%) in tinea cruris and corporis. Cure rates continued to increase up to four weeks after treatment, indicating that butenafine has residual therapeutic activity. In tinea pedis, twice daily application of butenafine for one week or once daily application for four weeks produces cure rates of up to 90%. Recent studies suggest that butenafine has inherent anti-inflammatory properties that can be useful in inflammation associated with dermatophyte infections, often achieved by the concomitant use of topical steroids.

Other drugs, which are used to treat the dermatophyte infections belong to two major classes; the azoles (e.g. clotrimazole, ketoconazole, oxiconazole, sulconazole, econazole and miconazole) and the allylamines (e.g. terbinafine and naftifine). In comparison, azoles are fungistatic, require a longer duration of therapy with twice daily applications, and do not possess post-treatment efficacy. Allylamines do not show rapid clearing of lesions, have low mycologic cure rates with higher relapse rates with similar dosing schedule. Additionally, the post-treatment efficacy of butenafine vouched for its potential to reduce recurrence even after premature discontinuation of therapy.

Tinea pedis: once daily application For 4 weeks or twice-daily application for 1 week.

Tinea cruris and Tinea corporis: Once daily application for 2 weeks.

Broad spectrum, fungicidal agent

keratinophillic and lipophillic

Achieves high mycologic and clinical cure rates with once daily application

Shorter duration of treatment

Shows an excellent post-treatment efficacy.

Well controlled studies have confirmed that butenafine has an excellent safety profile and tolerance. Most commonly occurring side effects is mild burning at the site of application. Pruritus, erythema, irritation and contact dermatitis were occasionally reported.

Butenafine, a new topical antifungal agent with broad spectrum, fungicidal activity and a shorter duration of therapy represents a step closer to the quest for an ideal topical antifungal agent.

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