Studies of analgesic drugs. VI. Comparative respiratory depressant activity of phenazocine and morphine.

Abstract

Phenazocine, the first benzomorphan compound to be used clinically, has been shown to be a potent analgesic in man. Early studies with this drug suggested that it possessed high analgesic potency, few respiratory or circulatory side effects, and low addiction liability In this study, the relative respiratory depressant activity of equivalent analgesic doses of phenazocine and morphine were determined in normal adult males. Although there was significantly less respiratory depression I hour after phenazocine than after morphine, this difference was small and probably not of clinical significance. Respiratory depression persisted 3 hours after phenazocine, whereas morphine depression was waning at this time. On the basis of respiratory effects, peak action of phenazocine occurred between 30 and 90 minutes after intramuscular administration, and it persisted longer than morphine.