Pharmacologic activity of β-endorphin in man

Human β-endorphin was administered i.v. to 3 patients with cancer pain and 2 undergoing withdrawal from methadone. Subjects also received morphine as a positive control and saline as a placebo. β-Endorphin (6-440 μg/kg) produced neither adverse clinical effects nor laboratory evidence of toxicity. Euphoria was not reported and catatonia was not observed. Two pain subjects reported good analgesia and mild improvement in mood. Independent observers indicated the drug was active. The other subject reported minimal pain relief; the observer noted evidence of moderate analgesia. A methadone dependent subject was studied during 9 days of complete narcotic abstinence. Twenty-five minutes after initiating an infusion of β-endorphin (440 μg/kg/30 min), the subject spontaneously reported complete relief of symptoms, and most of the objective signs of abstinence were reversed. The subject and observer, who both were unaware of the drugs administered, accurately identified morphine as a narcotic, and saline as a placebo. The subject reported that the effects of β-endorphin differed from those of morphine. Similar results have been observed in a second subject. These results indicate that there were no acute adverse effects associated with the doses of β-endorphin administered, and they also provide evidence that β-endorphin may possess analgesic and narcotic abstinence suppressing properties in man. Additional clinical trials with strict double-blind procedures are warranted.