Effect of Morphine , Meperidine , Diazepam and Ketamine on Pregnant Rat Uteri , in Vitro

Chong, Kyong Yi; Kim, Chi Hyo; Lee, Choon Hi

Abstract

For many years it had been universally taught that administration of the commonly used analgesic agents retards the progress of labor. It was therefore advised that these agents should not be administered until the labor was active and progress was rapid. In recent years, more scientific analysis of the progress of labor and accurate recording of uterine contractility revealed that this classical teaching was inaccurate. Despite the increasing use of regional analgesia during labor, systemic medications are still widely used to relieve pain and anxiety. There is no ideal, generally applicable analgesic agent for use during childbirth. All systemic medications used for pain relief in labor cross the placenta and may have a depressant effect on the fetus and injudicious administration of an overdose can cause some depression of uterine activity. It is suggested that elimination of pain or anxiety will decrease adrenal medullary release of epinephrine. Since epinephrine is a known inhibitor of uterine activity, a decrease in its serum level should lead to increased uterine activity. Thus it was decided to make an objective estimation of the effects of morphine, meperidine, diazepam and ketamine upon uterine contractility of pregnant rat uteri, in vitro. The results are as follows: 1) Morphine caused a significant concentration dependent decrease in the contractility of pregnant rat uteri. 2) Meperidene did not cause any significant change in the contractility of pregnant rat uteri. 3) Diazempam caused a concentration dependent decrease in the contractility and the contraction disappeared at a concentration of 80 ug/100ml. 4) Ketamine caused a significant concentration dependent decrease in the contractility of pregnant rat uteri. 5) Addition of CaCl2 to the K-H solution did not cause any significant change in the result.