The effects of a new opioid analgesic, meptazinol, on the respiration of the conscious rat.
In the conscious rat arterial PCO2 was measured as an index of respiratory status. The opioid analgesic meptazinol (7.5 - 30 mg kg-1) evoked small but significant increases in arterial PCO2 which were attenuated by naloxone. Meptazinol significantly reduced the increase in arterial PCO2 evoked by morphine. The respiratory depression induced by meptazinol, but not that induced by morphine, was enhanced by pretreatment with atropine. The (+)-enantiomer, but not the (-)-enantiomer of meptazinol increased arterial PCO2. In contrast, only the (-)-enantiomer reduced the respiratory depressant effect of morphine. It is proposed that the degree of respiratory depression induced by meptazinol is limited by its opioid antagonist and cholinomimetic properties.
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001381:Azepines / Q000494:pharmacology*; D002245:Carbon Dioxide / Q000097:blood; D008297:Male; D008621:Meptazinol / Q000494:pharmacology*; D009020:Morphine / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009294:Narcotics / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012119:Respiration / Q000187:drug effects*; D013237:Stereoisomerism; D013997:Time Factors
D001381:Azepines; D009292:Narcotic Antagonists; D009294:Narcotics; D002245:Carbon Dioxide; D008621:Meptazinol; D009020:Morphine; D001285:Atropine