randd THC- THE HIGHER THE DOSE, THE HIGHER THE HIGH But little correlation with plasma levels Six experienced marijuana users smoked cigarettes containing 1.32%, 1.97% and 2.54% 6 9 -tetrahydrocannabinol (THC) in a double-blind, cross-over trial. This corresponded to a mean THCconsumption of9.7, 12.8 and 16.0mg, respectively, and resulted in a dose-related peak THC plasma concentration, approximately 7-8 min after smoking began, despite continued inhalation. Peak plasma levels of the major metabolite (9carboxy-THC) occurred 22-28 min after smoking began. In subjective ratings of psychological 'highs', and in measurements of heart rate, again dose-related effects were observed, with maximum effects seen at I S-30 mins. These parameters both correlated more closely with plasma levels of 9-carboxy-THC than with THC, although other studies suggest a lack of pharmacological effect of the metobolite. In addition, subjective reports of drug effect for over 2 hours were reported, despite rapidly declining THC and 9-carboxy-THC levels. Although a distinct dose-related effect was seen, there was little apparent correlation with drug plasma levels, and the clinical conclusions which may be drawn solely from blood THC levels (such as in traffic accidents) are thus very limited. Perez-Reyes, M. et al.: Clinical Pharmacology and Therapeutics 31: 617 (May 1982)

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INPHARMA 19 Jun 1982

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