SCHOLL ALUMINUM CHLOROHYDRATE 25% OTC FOOT ANTIPERSPIRANT STUDIES
SCHOLL ALUMINUM CHLOROHYDRATE 25% OTC FOOT ANTIPERSPIRANT STUDIES cannot support a claim for that use, FDA OTC Div. Director William Gilbertson, PharmD, told the company in a June 10 feedback letter. The agency based its conclusion on analysis of four double-blind, randomized, bilateral comparison trials, each involving 12 female subjects. The studies compared the vehicle control with a 25% aluminum chlorohydrate solution (one study) or aerosol (three studies). Each subject also completed a questionnaire to assess wetness perception. Scholl submitted the studies to support a foot antiperspirant claim in October 1983. Aluminum chlorohydrate was included in the Tentative Final Monograph as a Category I underarm antiperspirant. Gilbertson said that the degree of sweat reduction found in the studies was "considerably below the 20% minimum level. . . required to assure a perceptible effect." When the studies were combined, "sweat reduction was demonstrated on 60% of the feet treated with the active drug," he noted. "Of this 60%, only 30% of the feet showed a sweat reduction over 15%, and 22% of the feet showed a reduction of 15% or less." There was an increase in sweat in the remaining feet treated with the active ingredient. Fifty-two percent of the feet in the placebo group showed a reduction in sweat; of these 19% had reductions above 15% and 33% reductions of 15% or less. The FDAer maintained the company's analysis of sweat reduction data is "based on arbitrarily chosen final sweat measurements and on arbitrary efficacy criterion (> 15% reduction from baseline) that was apparently defined after the data were collected." He added that the same criticism applies to Scholl's finding that 52% of subjects "showed 'clinically significant' differences in sweat production favoring the treated foot. That is, the particular sweat collections selected for analysis were not chosen consistently across studies, and the choice of a 5% difference as 'clinically significant was not prespecified in the protocol." Gilbertson explained that the agency reanalyzed the data "using the average of the two collections on day 4, or average of the four collections on day 4 and 5 as the baseline, and the average of the two final collections as a measure of final sweat production." Using analysis of covariance, Gilbertson said, "no significant differences were found between the effects of aluminum chlorohydrate and placebo in foot sweat production when analyzed by study, combined over all four studies, or combined over the three aerosol studies. Based on data from the four studies, no statistically significant treatment effect was found in sweat production or in subjects' perception of sweat."
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