Evaluation of pentamorphone in humans: a new potent opiate

We evaluated the analgesic properties of 14-beta-n-pentylaminomorphinone (pentamorphone), a new morphinan derivative, in 23 male volunteers divided into 6 groups who were given either placebo (1 per group) or 0.015, 0.03, 0.06, 0.12, 0.24, 0.48 microgram.kg-1 pentamorphone intravenously. Analgesia was evaluated by the maximal tolerance to a spring-loaded rod on the tibia and manubrium. Analgesic assessments and arterial blood samples were taken prior to and at set time intervals following drug administration. Pentamorphone produced a linear increase in pain tolerance with increasing dose as well as a dose-dependent depression of ventilation. Pentamorphone had no effect on blood pressure or heart rate in the doses used. Plasma histamine levels at 5 minutes were not elevated with any of the dosages. Pentamorphone appears to be an analgesic with clinically tolerable side effects in the range 0.12 to 0.24 microgram.kg-1 that merits further evaluation under clinical conditions.