Test‐retest stability of cardiovascular and subjective responses to intravenous cocaine in humans

Sixteen male i.v. cocaine users were measured on their cardiovascular and subjective responses to placebo followed on a separate day by 40 mg i.v. cocaine injections. They were retested within 2 weeks, again receiving placebo and 40 mg i.v. cocaine injections in a random order on separate days. Significant increases in baseline (pre‐injection) heart rates during the later sessions were interpreted as possibly reflecting conditioning effects. There were no significant differences in post‐injection increases in cardiovascular or subjective responses between the initial and later 40 mg conditions, which might have been indicative of tolerance or sensitization development. Test‐retest correlations, indicative of response stability, were moderate to high for any particular timepoint for blood pressure, heart rate, and subjective responses, but pre‐ vs. post‐injection change scores were stable across testings on these measures only under placebo. With the possible exception of some subjective responses, there was little evidence of test‐retest stability in responses (change scores) to the 40 mg cocaine injection.