THE EFFECT OF LEVORPHAN AND LEVALLORPHAN ON THE RESPIRATORY MECHANISM OF NORMAL MAN

¹ The Departments of Anesthesia, Medicine, and Physiology of the University of Rochester, School of Medicine and Dentistry, Rochester, New York

Levorphan is a severe respiratory depressant. Quantitatively it lowers the sensitivity of the respiratory center to CO₂ to about one half control. The threshold (apnea point) to CO₂ is raised about 4 mm. Hg. Levallorphan alone is also a respiratory depressant though it lowers the sensitivity to CO₂ less than levorphan and has no effect on threshold. When these two drugs are given together, ventilation is improved over that with either alone but is still less than control. Stimulus-response curves with subjects under the combination reveal that the sensitivity is restored to control value, but that the threshold remains at the same level as when under levorphan alone. The protective action of levallorphan was most apparent with high alveolar CO₂ tensions in these experiments.