Simultaneous administration of narcotic and narcotic-antagonist drugs in the newborn rabbit

The respiratory response of the newborn rabbit rendered acutely anoxic in nitrogen comprises periods of dyspnea, primary apnea, gasping, and terminal apnea. The duration of primary apnea is increased at the expense of the period of gasping by the prior administration of morphine and Pethidine * ; length of survival is not shortened. The simultaneous administration of Nalorphine † antagonizes this action of morphine but not of Pethidine; Levallorphan ‡ does not antagonize either morphine or Pethidine in comparable dosage. Described in this paper is the respiratory response of the newborn rabbit to acute anoxia when under the influence of various narcotic and narcotic-antagonist combinations. * Pethidine; Pethidine Hydrochloride; Meperidine Hydrochloride, U.S.P.; Demerol Hydrochloride. † Nalorphine Hydrochloride, U.S.P.; N-Allylnormorphine Hydrochloride. ‡ Levallorphan; N-allyl-3-hydroxymorphinan.