Tocolytic effect of morphine via increased metabolic clearance of oxytocin in the baboon

Young Hoon Bai, Sokcheon Pak, Bum Chae Choi, Laird Jr. Wilson

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)


Morphine is known to inhibit nocturnal uterine contractions in several animal models, and oxytocin is known to be a primary causative factor of uterine contractions. The purpose of the present study was to determine the tocolytic effect of morphine in relation to the pharmacokinetics of oxytocin, after a bolus injection of oxytocin. The metabolism of oxytocin was investigated during the third trimester in baboons. Four animals were placed on a tether system with venous and arterial access, including continuous uterine monitoring. Plasma oxytocin levels were determined by radioimmunoassay after extraction with petroleum ether/acetone. Morphine consistently increased the metabolic clearance rate of oxytocin in all four animals (p < 0.05) and this was in accordance with suppressed uterine contractions. We conclude that morphine could be used as an inhibitor of nocturnal uterine contractions, and that this is caused by the morphine induced increased metabolic clearance rate of oxytocin.
Original languageEnglish
Pages (from-to)567-572
Number of pages6
JournalYonsei Medical Journal
Publication statusPublished - 2002


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