Degree and duration of reversal by naloxone of effects of morphine in conscious subjects.

The effects of intravenous naloxone on several of the actions of intravenous morphine (mean dose 30 mg/70 kg) were studied in six volunteer subjects. Naloxone produced a well defined reversal of the respiratory depression, analgesia, and miotic and subjective effects of the morphine. The agonist action of morphine outlasted the antagonist action of a single dose of naloxone. The effect of repeated doses of naloxone was also short-lived, but continuous infusions were effective in maintaining reversal.