Naloxone-induced behavioral and physiological effects in normal and manic subjects.

Intravenous naloxone hydrochloride (20 mg) was administered to eight normal control subjects and 12 affective disorder patients manifesting manic or hypomanic symptoms. On two consecutive days, in a counterbalanced order, naloxone and placebo were given in a double-blind crossover design. The overall effect of naloxone was to decrease pulse rate and to promote lethargy and inactivation. The normal controls manifested reduced feelings of well-being, and the manic patients noted a subjective sense of slowing. There was a variable response pattern to naloxone in the manic patients in which four of the 12 patients manifested an observable reduction in their manic symptoms and behavior after the naloxone administration. Naloxone seems to have had a nonspecific subduing effect in both normal subjects and patients and may also have had a selectively greater effect in a small subsample of the manics.