Effects of heroin and naltrexone on plasma prolactin levels in man.

Plasma levels of prolactin were increased following intravenous self-administration of heroin by young men with a history of heroin addiction. Following 10 days of controlled heroin usage, tolerance could be demonstrated to the acute prolactin-releasing effect of heroin. There was no evidence that a single dose of naltrexone affected basal prolactin levels.