Naloxone: dose-dependent antagonism of respiratory depression by fentanyl in anaesthetized patients.

Naloxone was used to antagonize the respiratory depression caused by the administration of fentanyl 0.05 mg to patients anaesthetized with 0.5% halothane in 70% nitrous oxide in oxygen. Four groups of at least 10 patients each were studied. Doses of 0.1, 0.2 and 0.4 mg of naloxone were given, and an effect proportional to the logarithm of the dose was demonstrated.