Growth inhibition of Malassezia species by pharmacological concentrations of polidocanol.

In vitro antifungal properties of polidocanol (Thesi), a hydroxypolyethoxydecan, were investigated against various yeasts at concentrations of 0.05-10% (w/w) by means of the agar diffusion test; in the case of lipophilic Malassezia furfur, polidocanol-containing olive oil was used additionally for sensitivity study. Six strains of M. furfur of different clinical origin were tested as well as strains of C. albicans (3), C. krusei (3), C. parapsilosis (2), C. robusta (2), Tr. cutaneum (2) and one strain each of C. guilliermondii, C. glabrata, C. tropicalis and M. pachydermatis. Both test systems revealed predominantly fungistatic activity against M. furfur, with a minimal inhibitory concentration (MIC) of 1% polidocanol (w/w), while yeasts of other genera (Candida species, Trichosporum species) showed no or only transitory (C. krusei) inhibition of growth. M. pachydermatis was also found to be sensitive with a MIC of 0.1%; this suggests a specific inhibitory effect against the genus Malassezia. Polidocanol, which has been used for decades as an antipruritic and analgesic in various topical preparations at concentrations between 3% and 5%, might therefore be suitable for prophylaxis of recurrent pityriasis versicolor or in veterinary medicine.