Tocolytic Effect of Morphine via Increased Metabolic Clearance of Oxytocin in the Baboon.
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.
Bai
Young Hoon
YH
Research Division of Biological Science, College of Medicine, Chosun University, Gwangju, Korea.
Pak
Sok Cheon
SC
Choi
Bum Chae
BC
Wilson
Laird
L
D000818:Animals; D005260:Female; D008657:Metabolic Clearance Rate; D009020:Morphine / Q000494:pharmacology*; D010121:Oxytocin / Q000493:pharmacokinetics*; D010215:Papio; D011247:Pregnancy; D015149:Tocolytic Agents / Q000494:pharmacology*; D014590:Uterine Contraction / Q000187:drug effects
D015149:Tocolytic Agents; D010121:Oxytocin; D009020:Morphine