Effect of Pethidine on the Contractility of Myometrial Strips from Human Term Gravid Uterus in Vitro

Abstract

The effect of pethidine on the contractility of myometrial strips was stud ied in vitro. Myometrial strips were taken from the lower segment of 32 term par turients, undergoing low transverse caesarean section at Siriraj Hospital. Nine par turients were excluded from the study because their myometrial strips showed no spontaneous contraction in vitro. Of the 23 parturients with active strips, 10 were in latent phase and 13 were in active phase. The myometrial specimen from each parturient was divided into 2-6 small strips of equal size which were then randomly used as either control or experimental strips. The pattern of isotonic contraction was studied. In comparison with the time-matched control, pethidine in therapeutic concentrations (0.25, 1, and 4 ug/ml) did not exert any effect on the amplitude and period of myometrial contraction. However, at the extra-high concentration of 40 ug/ml, which was 160 times greater than the therapeutic serum level, pethidine low ered the amplitude or strength of myometrial contraction in the active phase group, while the period of contraction was shortened in both the active and latent phase groups. Further study is suggested to confirm these effects in vivo. (Thai J Obstet Gynaecol 1992; 4: 1-6.)