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HRG PETITION TO BAN IODOCHLORHYDROXYQUIN BASED ON UNCONTROLLED

Executive Summary

HRG PETITION TO BAN IODOCHLORHYDROXYQUIN BASED ON UNCONTROLLED and inadequate toxicity studies in dogs, Ciba-Geigy asserted in recent comments on the Health Research Group's June petition. The dog study on which HRG based its petition "is not an adequate and well controlled safety trial," Ciba-Geigy asserted, because "comparative conclusions regarding hepatotoxicity and weight loss are made with respect to the animals treated as compared to control animals, but nowhere do the authors expiain the nature and extent of the control procedures utilized. Ciba-Geigy maintained that unless "the control animals were from the same source and shipment as treated animals; randomly assigned to treatment groups; and treated with placebo vehicle to preclude effects from handling, anesthesia, surgical techniques and blood withdrawal; then the entire study is by definition flawed and its results unreliable." The firm asserted that the nature of the hepatotoxicity in the dog study is more likely "the result of incidental diseases to the test animals rather than clioquinol therapy." HRG requested that FDA remove all Rx and OTC products containing iodochlorhydroxyquin (previously called clioquinol) from the market, maintaining that they are "dangerous to infants and adults," based on the results of a 1984 University of Nebraska dog toxicity study which found that "long-term application. . . can result in sufficient absorption to produce hepatotoxicity" ("The Pink Sheet" July 29, T&G-9). The ingredient is in Ciba-Geigy's OTC Vioform and its Rx Vioform HC, as well as other branded and generic products. FDA has claimed that Vioform HC is less than effective. A DESI hearing on the drug, originally shceduled for April, was rescheduled for November. A second study cited in HRG's petition concluded that 40% of iodochlorhydroxyquin applied to the skin is absorbed percutaneously. Ciba-Geigy asserted that the 40% absorption rate was obtained by methods "that will greatly overestimate the absorption rate." According to Ciba-Geigy, the study determined absorption by measuring the remaining amount of cream on subjects' forearms 12 hours after application. That method, Ciba-Geigy maintained, overestimates absorption because "most of the drug will remain undetected on the skin in the insoluble residue of the cream." The firm also argued that FDA's OTC Antimicrobial (II) Panel "found clioquinol to be safe as a topical OTC product," based on studies with "plasma levels in the same range as shown in "the absorption study cited" by HRG. "Contrary to the petitioner suggestion," the absorption study does "not represent new data not otherwise before the Panel," Ciba-Geigy maintained.

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