Naloxone does not affect pain sensitivity, mood or cognition in patients with high levels of beta-endorphin in plasma

Patients with either Cushing's or Nelson's syndrome, both of which are associated with markedly increased levels of beta-endorphin immunoreactivity in plasma, were given tests of pain sensitivity, mood, and cognition following administration of 10 mg naloxone and saline on separate days. No differences were found between naloxone and saline administrations on any of these psychological measures. These results suggest that immunoreactive beta- endorphin in plasma does not exert opiate effects.