[Effect of keratin on the efficacy of fluconazole]

Development of topical therapeutics for management of onychomycosis and other nail disorders: a pharmaceutical perspective

The human nail plate is a formidable barrier to drug permeation. Development of therapeutics for management of nail diseases thus remains a challenge. This article reviews the current knowledge and recent advances in the field of transungual drug delivery and provides guidance on development of topical/ungual therapeutics for management of nail diseases, with special emphasis on management of onychomycosis, the most common nail disease. Selection of drug candidates, drug delivery approaches, and evaluation of formulations are among the topics discussed. A comprehensive mathematical description for transungual permeation is also introduced.

Study of in vitro drug release and percutaneous absorption of fluconazole from topical dosage forms

The present study aimed to evaluate different dosage forms, emulsions, emulgels, lipogels, and thickened microemulsion-based hydrogel, as fluconazole topical delivery systems with the purpose of determining a formulation with the capacity to deliver the whole active compound and maintain it within the skin so as to be considered a useful formulation either for topical mycosis treatment or as adjuvant in a combined therapy for Cutaneous Leishmaniasis. Propylene glycol and diethyleneglycol monoethyl ether were used for each dosage form as solvent for the drug and also as penetration enhancers. In vitro drug release after application of a clinically relevant dose of each formulation was evaluated and then microemulsions and lipogels were selected for the in vitro penetration and permeation study. Membranes of mixed cellulose esters and full-thickness pig ear skin were used for the in vitro studies. Candida albicans was used to test antifungal activity. A microemulsion containing diethyleneglycol monoethyl ether was found to be the optimum formulation as it was able to deliver the whole contained dose and enhance its skin penetration. Also this microemulsion showed the best performance in the antifungal activity test compared with the one containing propylene glycol. These results are according to previous reports of the advantages of microemulsions for topical administration and they are very promising for further clinical evaluation.

Topical delivery of fluconazole: in vitro skin penetration and permeation using emulsions as dosage forms

We investigated in vitro skin penetration and permeation of fluconazole from emulsions containing different penetration enhancers. Fluconazole permeation was high (15-65% of the applied dose) across hairless mouse skin and low (8-9%) across pig ear skin. Permeation across mice skin from a formulation containing propyleneglycol and isopropyl myristate was significantly higher than that observed with the paraffin oil and propyleneglycol or Transcutol emulsions. With pig skin, the paraffin oil or isopropyl myristate and propyleneglycol emulsions showed similar skin permeation and penetration. However, these emulsions provided epidermal concentrations higher than the minimal inhibitory concentrations for most dermatophytes.

Binding of doxycycline to keratin, melanin and human epidermal tissue

Doxycycline is licensed for the prophylaxis of malaria and recent research has indicated the feasibility of delivering this drug across the skin. The binding of doxycycline to keratin could influence skin permeation rates and it has been suggested that the interaction of anti-malarials with melanin may contribute to side effects, such as retinal damage. Doxycycline HCl was incubated with keratin (bovine horn), melanin (Sepia officinalis) and human epidermal samples (native and delipidised). Dose dependent binding of doxycycline to keratin and melanin was observed, and was of similar magnitude for each protein. However, the binding of doxycycline to melanin was lower by an order of magnitude relative to data previously reported for some other anti-malarials, and may indicate reduced side-effects. Doxycycline also demonstrated significantly greater affinity for native epidermal skin than for delipidised skin showing that doxycycline, a charged polar molecule, has affinity for the intercellular lipid matrix in addition to the proteinaceous domain. For native skin it was estimated that saturation would be reached at approximately 140 microg x cm(-2); for delipidised skin it was estimated to be 60 microg x cm(-2). Overall, the data suggested that the partition-diffusion steps that are involved in transcellular permeation are possible.