Canadian Journal of Anesthesia, Vol 16, 151-161, Copyright © 1969 by Canadian Anesthesiologists' Society

The Respiratory, Circulatory, and Narcotic Antagonistic Effects of Nalorphine, Levallorphan, and Naloxone in Anaesthetized Subjects

¹ Division of Anesthesiology, Montefiore Hospital and Medical Center, and Department of Anesthesiology, Albert Einstein College of Medicine, Bronx, New York

Nalorphine (150 µg/kg) and levallorphan (20 µg/kg), when administered to lightly anaesthetized subjects who had not received a narcotic, caused significant depression of respiratory rate and minute volume. In contrast, 5 and 10 µg/kg naloxone caused no respiratory depression. These doses of nalorphine, levallorphan, and naloxone caused a moderate decrease of pulse rate and systolic blood pressure. Naloxone 5 and 10 µg/kg offered significantly greater protection against the respiratory depressant effects of 20 µg/kg oxymorphone administered five minutes later than 150 µg/kg nalorphine or 20 µg/kg levallorphan. None of the three narcotic antagonists affected the oxymorphone-induced decrease of pulse rate, and all had about the same protective effect against the fall of systolic blood pressure caused by this compound. Since doses of naloxone, which provide significantly better protection against narcotic-induced respiratory depression than the conventional doses of nalorphine and levallorphan, cause no respiratory depression in themselves, it should be considered the narcotic antagonist of choice for clinical use.