Effect of naltrexone on apnea of prematurity and on plasma beta-endorphin-like immunoreactivity.

Plasma levels of beta-endorphin-like immunoreactivity (beta-ELI) were measured in premature infants with apnea (n = 11) and compared to those in nonapneic controls (n = 9). Naltrexone (1-3 mg/kg) was given to the infants with apnea, 6 of whom were also receiving methylxanthines. Chest wall movements, nasal airflow, transcutaneous PO2 and electrocardiogram were recorded for 4-6 h prior to and for 4-6 h after administration of naltrexone. Samples for beta-ELI were taken prior to and 1 h post naltrexone. beta-ELI levels were significantly higher (p less than 0.007) in infants with apnea of prematurity than in control infants. No significant difference was found in beta-ELI levels before and after naltrexone. Naltrexone did not decrease the incidence of apnea.