Drugs under experimental and clinical research
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Dextromethorphan, after administration, is rapidly and extensively transformed into dextrorphan. The aim of this study was to compare the cough-suppressing activity of 6, 12, 24, 48 mg/kg, i.p., of dextrorphan (dextro rotatory isomer of racemorphan) with that of dextromethorphan, using the model of citric acid-induced coughing in the unanaesthetized, unrestrained guinea pig. ⋯ However, at 48 mg/kg, i.p., dextromethorphan had a toxic effect while dextrorphan did not. Because dextrorphan is the major metabolite of dextromethorphan and has antitussive activity comparable to that of dextromethorphan, clinical use of dextrorphan is suggested.