Intranasal cocaine: dose relationships of psychological effects and plasma levels.

We compared the psychological effects of three doses of intranasal cocaine hydrochloride (.2, .75, and 1.5 mg/kg) with cocaine plasma concentrations in four volunteers. Intranasal lidocaine hydrochloride (.2 mg/kg) was used as a topically active placebo. Peak "high" ratings were related to both dose and peak plasma concentrations. At a given plasma concentration, "high" ratings were greater when plasma levels were increasing than when they were decreasing. This indicates that acute tolerance by tachphylaxis occurred after single doses. The cocaine "high" was a pleasant feeling but was without distinctive sensations. The dramatic effects of intranasal cocaine on the street may be related to larger or repeated doses as well as the setting.