Naloxone does not antagonize general anesthesia in the rat

The administration of naloxone 2, 10, 50, or 250 mg/kg intravenously did not alter halothane requirement (MAC) in Sprague-Dawley rats (12 per group). Two rats convulsed when given 50 mg/kg while anesthetized with halothane. In a separate group of awake rats, seven of nine animals convulsed when given naloxone, 100 mg/kg. It is concluded that any effect of naloxone on anesthetic requirement must be small (not significant in our study), and that if an effect exists it is the result of a nonspecific analeptic action of naloxone rather than a specific action at opiate receptors.