TOPICAL IODOCHLORHYDROXYQUIN-CONTAINING PRODUCTS SHOULD BE MARKETED ON Rx BASIS ONLY, FDA CMTE. CONCLUDES; BLACK BOXED WARNING AGAINST USE IN INFANTS IS SUGGESTED
Topical iodochlorhydroxyquin-containing products should be available solely by Rx, FDA's Dermatologic Drugs Advisory Cmte. recommended Nov. 18. The cmte., expressing concern about the potential for misuse, agreed that all OTC iodochlorhydroxyquin-containing products should be removed from the market. Cmte. member Wilma Bergfeld, MD, Cleveland Clinic, also emphasized the "possibility of a threat to the infant," and recommended that Rx labeling include a black boxed warning against use in infants. The American Academy of Pediatrics has also recommended the ingredient not be used in the pediatric population. In his presentation to the cmte., Health Research Group Director Sidney Wolfe cited a Nov. 8 letter from the academy to FDA in which the academy stated "there is no question" that iodochlorhydroxyquin "can be absorbed through the skin, particularly if the skin's integrity has been compromised as in the case of diaper rash." Iodochlorhydroxyquin, also known as clioquinol, is found in Ciba-Geigy's OTC product Vioform, as well as the firm's Rx drug (ITALICS)Vioform HC (hydrocortisone). Ciba-Geigy Exec Director-Medical Services Marvin Wetter, MD, commented that "regarding the use in infants, ]Ciba-Geigy[ would be willing to explore that at greater lengths with" FDA. Wetter also noted that OTC sales account for 50% of total Vioform sales. FDA requested the cmte.'s recommendations on marketing of iodochlorhydroxyquin in light of a petition by the Health Research Group requesting the removal of all Rx and OTC drugs containing the ingredient. The petition, filed in June, was based on a 1984 University of Nebraska dog toxicity study. University of Nebraska investigator Sidney Stohs, MD, reported that 3% iodochlorhydroxyquin cream was applied twice daily for 28 days to the shaved skin of five dogs. Stohs said there was "extensive absorption of the drug based on the amount remaining on the skin and the amount excreted in urine and feces . . . and ]found in[ tissue concentration studies." He concluded, based on liver pathology, weight loss, and an incidence of leg paralysis in one dog, that the drug is toxic with long-term topical application. Cmte. member Neal Penneys, PhD, University of Miami, asserted that Stohs' investigation was not "a very good study." He said the control animals were not mentioned until the end of the results section of the study "and there is no mention of the way they are treated." He also questioned why only one dog was studied for drug excretion in the feces, and why three dogs were given an I.V. dose of the drug after a wash-out period. American Academy of Dermatology representative Peyton Weary, MD, criticized both the dog study and a University of Nebraska study of humans treated 12 hours with topical 3% Vioform. "The maximization of absorption by the use of occlusive dressings in both studies . . . is clearly unlike the use of these products in patient care," Weary stated. He also commented that "the liver toxicity studies in dogs were performed after intravenous administration of the drug and are clearly not applicable to the prevailing usage pattern of these products." Weary recommended that until the issue of potential toxicity is resolved, topical OTC iodochlorhydroxyquin products should be removed from the market. He suggested that "more appropriate studies of the percutaneous absorption of iodochlorhydroxyquin in both man and animals" be conducted, "including studies . . . of liver toxicity, as well as neurologic abnormalities." In addition, "a retrospective analysis of all cases of subacute myeloopticneuropathy occurring in the last five years in 20 major academic medical centers should be undertaken to determine if any of these individuals have been users of iodochlorhydroxyquin products," Weary stated. He said such a study could be completed within six months.
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