HAIR STRAND TEST 269 2 4 8 Figure 2. Growth ofM. globosa CBS 7966 after 18-day incubation hair from ten volunteers pre-incubated in andidandruff shampoo (A) (growth 1/10 Co = control). markedly lower concentration compared with that of climbazole, but may also be a specific feature of the substance, which is revealed by the hair strand test. Previous in vitro studies have shown hydroxypyridones to be highly effective against Malassezia spp., but data on their bioavailability in/on human hair are not yet available this also applies to the other agents tested. The polidocanol concentrations used should actually have had an inhibitory effect (18), but probably this substance, too, does not bind to human hair, so that such an effect could not be demonstrated. Tests using higher concentrations might be reasonable. CONCLUSION In summary, the in vitro hair strand test was found to be an interesting and reliable new test model for evaluation of the antifungal activity of antidandruff preparations, espe- cially with regard to a possible depot effect. Climbazole proved to be effective. With all other agents, no bioavailability from the hair was found, possibly because of the low concentrations used. Other substances (e.g., zinc pyrithione, ketoconazole, selenium disulfide, tar) are currently tested with the new system. The current test model does not primarily assess binding of antimycotics to scalp keratin. Active ingredients might rediffuse from the compartment of the hair to influence the growth of Malassezia yeasts on the sebum-rich scalp surface. Supplementary examination of the hair samples by GC-MS analysis would substantiate the validity of the test system. The hair strand test could also be performed ex vivo with hair samples from volunteers who regularly use

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