Naloxone or haloperidol but not yohimbine reverse apomorphine-induced respiratory depression.

Intravenous injection of low doses of naloxone was found to reverse the respiratory depression induced by apomorphine in chloralose-anesthesized dogs. Similar results were obtained with haloperidol, whereas yohimbine remained ineffective. These data suggest that apomorphine depresses respiratory rate through a mechanism involving both dopamine and opiate mechanisms but not alpha 2-adrenoceptors. Respiratory arrest induced by overdosages of apomorphine can be treated with naloxone.