Plasma adrenocorticotropin responses to opioid blockade with naloxone: Generating a dose-response curve in a single session

We examined two methods of generating a dose-response curve to the opioid r eceptor antagonist naloxone. In 15 healthy male subjects (18-25 years) plas ma adrenocorticotropin (ACTH) responses to five doses of naloxone studied o ver 5 separate days were compared to plasma ACTH responses to five incremen tal doses of naloxone studied within a single session. There was a statisti cally significant positive correlation in ACTH responses (area under the cu rve and peak) between dosing methods, Furthermore, the doses of naloxone th at produced half-maximal and maximal ACTH response were similar. The compar ability of ACTH responses between the two naloxone dosing techniques, combi ned with the safety and ease associated with the single-session methodology , underscores the usefulness of the single-session technique for future inv estigations. (C) 2000 Society of Biological Psychiatry.