Naloxone decreases the duration of primary apnea with neonatal asphyxia.

Naloxone, a specific opiate antagonist with no agonist properties, in doses of 0.4 and 4.0 mg/kg was found to markedly reduce the duration of primary apnea in asphyxiated newborn rabbits. There was no effect on the duration of the hyperpneic phase (time to primary apnea) or on survival time (time to last gasp). It is suggested that endogenous opiate-like peptides are released during asphyxia and are the major factor in the suppression of medullary inspiratory neuronal discharge during primary apnea.