Serum concentrations of PRL, GH, LH, FSH, TSH and cortisol after single administration to man of a new synthetic narcotic analgesic butorphanol.

The i.m. administration to 6 healthy adult male volunteers of 2 mg butorphanol, a potent synthetic opiate analgesic, resulted in a significant rise in serum PRL level, without affecting GH, LH, FSH, TSH or cortisol secretion. These effects indicate that in man butorphanol exerts an opiate agonist rather than an opiate antagonist effect at the hypothalamic and/or pituitary level.