DOXYLAMINE TWO-YEAR RAT CARCINOGENICITY STUDY IS UNDERWAY
DOXYLAMINE TWO-YEAR RAT CARCINOGENICITY STUDY IS UNDERWAY at the Natl. Center for Toxicological Research (NCTR). The study, which began in April, follows completion of a 14-day repeated dose study and a 90-day subchronic study. Summary results of the studies were published in the Natl. Toxicology Program's (NTP) 1984 annual plan. According to the program report, data from the 90-day study "indicate fatty changes and cytomegaly in livers and parotid salivary glands of rats and cytomegaly and karyomegaly in the livers of mice." An additional two-year mouse study is scheduled to begin shortly. Doxylamine was recommended by FDA as a candidate for carcinogencity testing at the NCTR because of its similarity to methapyrline, which was withdrawn from the market after studies found the drug carcinogenic in rats. The NTP report notes that similar 14-day and 90-day NCTR studies have been conducted with the antihistamine pyrilamine. NCTR has also conducted several studies with caffeine, including the acute toxicity study and the 14-day repeated dose and 90-day subchronic studies. According to the NTP report "no dose related effects were observed in serum levels of hepatic enzymes" in the 90-day study and "there were no significant gross lesions observed in either rats or mice." The report added that "microscopically there was a dose related effect in rats with higher dose groups exhibiting alterations in the parotid and submaxillary salivary glands." However, "there were no treatment related lesions in mice, though salivary gland parenchymal cells often had abundant stored secretory granules." The NTP annual plan describes the toxicology research, test development, and chemical testing underway at the Natl. Institutes of Health's Natl. Institute of Environmental Health Sciences; FDA's Natl. Center for Toxicological Research; and the Centers for Disease Control's Natl. Institute for Occupational Safety and Health. It also explains NTP's strategy for testing, test methods development and validation and details NTP's accomplishments in the preceding fiscal year. Copies of the document are available from NTP's Public Information Office, P.O. Box 12233, Research Triangle Park, NC 27709 (919-541-3991).
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