This study evaluated the antifungal efficacy of a 2% climbazole shampoo against 3 Malassezia spp strains using a modified hair strand test.
Healthy research dogs (n = 6) were bathed with either a 2% climbazole shampoo or a physiologic hygienic shampoo. Hair strands (ie, clipped hairs) were collected before and after treatment at several predetermined time points for 30 days posttreatment. At day 30, the climbazole-treated dogs were bathed with the physiologic hygienic shampoo, and further hair strands were collected at predetermined time points over an additional 25 days. Hairs were placed on Sabouraud dextrose agar plates streaked with Malassezia pachydermatis, and inhibition zones were measured.
Antifungal activity, noted within 5 hours of application of the 2% climbazole shampoo, was sustained for 30 days. The maximum inhibition zone was observed on day 4. No zones of inhibition were noted around hairs from dogs bathed with the physiologic hygienic shampoo. On day 30, the climbazole-treated dogs were bathed with the physiologic cleansing shampoo, and there was a temporary increase in zones of inhibition around the hairs. This increase may have been caused by release of lipophilic climbazole trapped in skin appendages. All dogs tolerated the climbazole product; no adverse events were reported. The authors concluded that the modified hair strand technique is a useful assay of the bioavailability of the active ingredients in topical formulations and that there is persistent antifungal activity of dog hairs treated once with 2% climbazole shampoo.