Intravenous cocaine infusions in humans: dose responsivity and correlations of cardiovascular vs. subjective effects.

Eight experienced IV cocaine users were intravenously administered 0, 10, 20, and 40 mg of cocaine hydrochloride on separate days in a pseudo-randomized ascending dose series, such that the 20 mg dose always preceded the 40 mg dose. They were subsequently administered 0, 20, and 40 mg of cocaine in a fully randomized presentation order. Cardiovascular effects of cocaine were significantly different from placebo for the 20 mg, but not the 10 mg dose, in contrast to subjective responses which differed from placebo for the 10 mg dose. Cardiovascular and subjective effects of cocaine did not differ between the 20 and 40 mg dose conditions for the pseudo-randomized trials, but did differ in the fully randomized trials. This lack of difference in responsivity between the 20 and 40 mg dose in the earlier trials may possibly have been due to contrast effects. Cardiovascular responses were not consistently correlated with subjective responses, either within a cocaine dose condition or across doses.