Plasma levels of diazepam and mood ratings

Ten subjects received 10 and 20-mg. doses of diazepam intravenously. The plasma levels of the drug and its major metabolite, desmethyl-diazepam were measured and coordinated with answers to a subjective questionnaire. After initial rapid decline of the diazepam level, the level and shape of the remaining part of individual plasma curves showed considerable variance. Increases in diazepam levels were minute (0.04 plus or minus 0.03 mcg./ml.). Desmethyl-diazepam levels continued to build up until the end of sampling. Contrary to some previous reports, no recurrent drowsiness was evident after initial recovery. Correlation between plasma levels of diazepam and some of the subject's moods was significant. Nevertheless, further studies are needed to determine whether plasma levels can be meaningfully related to various cerebral effects of the drug.