A comparison of bifonazole and ciclopiroxolamine: in vitro, animal, and clinical studies

Common Fungal Infections of the Feet in Patients with Diabetes Mellitus

Superficial fungal infections of the foot (tinea pedis and onychomycosis) are common among elderly patients. Although most authorities believe that patients with diabetes mellitus have an increased predisposition to dermatophytic infections, some controversies still remain. Because these infections disrupt the skin integrity and provide an avenue for bacterial superinfection, elderly diabetic patients with dermatophytic infection should be promptly treated with an antifungal agent. For most dermatophytic infections of the foot, topical agents are usually effective and less expensive than oral agents. Laboratory diagnosis of fungal infection prior to institution of therapy is recommended. Proper technique for obtaining the specimen is important to ensure a higher chance of isolating the infecting fungus. Commonly used anti-dermatophytic agents that are also active against the yeasts include the imidazoles, the allylamines-benzylamines and the hydroxypyridones, which are also effective against most of the moulds. Oral therapy for tinea pedis, although not well studied, should be limited to patients with more extensive infections, such as vesicobullous and moccasin type, resistant infections or chronic infections. In addition, oral agents should also be considered in diabetic and immunosuppressed patients. On the other hand, treatment of onychomycosis of the foot usually requires systemic therapy. Griseofulvin is the least effective agent when compared with the newer agents. Terbinafine, itraconazole and fluconazole have been shown to have acceptable cure rates. More recently, topical treatment of the nail with 8% ciclopirox nail lacquer, bifonazole with urea and amorolfine have been reported to be successful. Over the past decade, fungal foot infections of the skin and nail are more effectively treated with the introduction of numerous topical and oral agents.

The hydroxypyridones: a class of antimycotics of its own

The hydroxypyridones chemically form a class of antimycotics not related to others. For a long time ciclopirox olamine has been the only compound to be used clinically. Recently, ciclopirox as a free acid and rilopirox have also been considered. The congeners are active against a broad spectrum of medically relevant fungi including dermatophytes, yeasts and moulds in vitro. According to investigations based on animal and in vivo models for fungal disease, this also applies in vivo. Low toxicity in the experimental animal has made topical applications in man possible. Clinical experience relates, in particular, to dermatophytosis and vaginal candidosis, but rarer conditions have also been investigated. High tolerability corresponds to efficacy in major dermatomycological conditions. Today, interest mainly focuses on ciclopirox lacquer for onychomycosis. Here as in general, the relative role of hydroxypyridones will have to be finally established in comparative trials.

Efficacy of 6-amino-2-n-pentylthiobenzothiazole on Trichophyton in vitro and in vivo

In vitro and in vivo antifungal activities of synthetically parepared 6-amino-2-n-pentylthiobenzothiazole (APB) against Trichophyton strains were studied. APB inhibited the growth of 3 Trichophyton strains at 65 micrograms/ml. 2-Mercaptobenzothiazole was not effective at 125 micrograms/ml and ketoconazole inhibited the growth at 20-30 micrograms/ml. Treatment of experimental dermatophytosis in guinea pigs using 2.5% APB cream was studied in comparison to Canesten cream (1% clotrimazole). Dermatophytosis was considerably reduced after both APB and Canesten therapies.

The dermatophytes

The etiologic agents of the dermatophytoses (ringworm) are classified in three anamorphic (asexual or imperfect) genera, Epidermophyton, Microsporum, and Trichophyton. Species capable of reproducing sexually belong in the teleomorphic genus, Arthroderma, of the Ascomycota. On the basis of primary habitat association, they may be grouped as geophilic (soil associated), zoophilic, and anthropophilic. Adaptation to growth on humans by most geophilic species resulted in diminished loss of sporulation, sexuality, and other soil-associated characteristics. The dermatophytes have the ability to invade keratinized tissue (skin, hair, and nails) but are usually restricted to the nonliving cornified layer of the epidermis because of their inability to penetrate viable tissue of an immunocompetent host. However, invasion does elicit a host response ranging from mild to severe. Acid proteinases, elastase, keratinases, and other proteinases reportedly act as virulence factors. The development of cell-mediated immunity correlated with delayed hypersensitivity and an inflammatory response is associated with clinical cure, whereas the lack of or a defective cell-mediated immunity predisposes the host to chronic or recurrent dermatophyte infection. Chronic dermatophytosis is mostly caused by Trichophyton rubrum, and there is some evidence that mannan produced by this fungus suppresses or diminishes the inflammatory response. Since dermatophytes cause a communicable disease, modes of transmission and control are discussed as well as a survey of recent trends in therapy. Collection of specimens, culture media, and tests for identification are also presented. Genetic studies have led to an understanding of incompatibility mechanisms, pleomorphism and variation, resistance to griseofulvin, and virulence. Molecular biology has contributed to our knowledge of the taxonomy and phylogenetic relationships of dermatophytes.

Efficacy of ciclopiroxolamine 1% cream in onychomycosis and tinea pedis

Ciclopiroxolamine is now under use as an antifungal agent for about a decade. Its activity is well-known in moderate climates, but there is a lack of knowledge on the activity in tropical and subtropical areas. 49 patients suffering from onychomycosis (42) and/or tinea pedis (33) were enrolled in a clinical trial in Taiwan. The patients received ciclopiroxolamine 1% cream 2-3 times a day for 3 to 24 month. In addition, infected nails were filed to facilitate drug penetration. In onychomycosis, 14% of the patients were cured and another 36% improved. One patient relapsed after 10 months. Cure was achieved more easily, if there were only modest alterations of the nail plate. With respect to tinea pedis the results were more favourable, the cure rate was 42%, another 45% of the patients improved. Following this dosage regimen, side effects did not occur. The results show onychomycosis to be highly resistant to antifungal therapy, perhaps even more as compared to tinea pedis in temperate climates. The good tolerability favours topical ciclopiroxolamine for this recalcitrant disease.

Experimental dermatophytosis in nude guinea pigs compared with infections in Pirbright White animals

With this investigation we wanted to compare the suitability of two different strains of guinea pigs to evaluate topical antifungals after experimental Trichophyton mentagrophytes infection. The "hairless"-strain was compared with the hairy Pirbright White strain. The infection areas were treated with a skin retention test (application before infection) and two sets of therapy tests (application after infection). In the retention test the different antimycotic compounds led to better gradations. Also, in the two sets of therapy tests the gradations among the compounds were more clearly and more comparable to published results of clinical trials. In the histological investigations the infections in the "hairless" animals developed in a way which is known from dermatophytoses in human skin. In the Pirbright White strain, however, due to the adjacent hair roots, a marked inflammatory reaction of the tissue persisted for 3 weeks which is not observed on human skin of the trunk and extremities. We, therefore, consider the "hairless" strain of guinea pigs to be more suitable than hairy animals for the comparison of topical antimycotics.

Bifonazole. A review of its antimicrobial activity and therapeutic use in superficial mycoses

Bifonazole is a substituted imidazole antifungal agent structurally related to other drugs in this group. It possesses a broad spectrum of activity in vitro against dermatophytes, moulds, yeasts, dimorphic fungi and some Gram-positive bacteria. Both non-comparative and comparative clinical trials have clearly demonstrated the efficacy and safety of various formulations of bifonazole 1% (cream, gel, solution and powder) applied once daily in the treatment of superficial fungal infections of the skin such as dermatophytoses, cutaneous candidiasis and pityriasis versicolor. In comparative studies bifonazole was significantly superior to placebo and at least as effective as alternative imidazole antifungal drugs including clotrimazole, econazole, miconazole, oxiconazole and sulconazole. Preliminary studies in other superficial skin and nail infections/dermatoses suggest that bifonazole may be useful for treating onychomycoses (in a combination cream; bifonazole 1% plus urea 40%), otomycoses, erythrasma, sebopsoriasis, seborrhoeic dermatitis and rosacea. However, controlled trials are needed in each of these clinical settings to assess accurately its relative place in therapy. Thus, bifonazole is an effective and well-tolerated treatment for superficial fungal infections of the skin. Compared with the majority of topical antifungal drugs, which need to be applied at least twice daily, bifonazole offers the convenience of once daily administration, which may improve patient compliance.