Effect of intrathecal fentanyl on oxytocin secretion in pregnant women notin labour

We studied the effects of spinal intrathecal fentanyl on oxytocin secretion in 20 healthy women prior to an elective caesarean delivery at term under spinal anaesthesia. The women were randomly allocated into two groups with respect to spinal anaesthesia. Group I (n = 10) received intrathecal bupiva caine (15 mg) plus fentanyl (25 mug), and Group II (n = 10) received intrat hecal bupivacaine (15 mg) alone, prior to caesarean section. The two groups were comparable demographically. Altogether, ten samples of 4.5 ml of bloo d (taken every 60 s) were obtained before and ten samples were obtained aft er the intrathecal administration of the drug and establishment of the T6 b lock, and plasma oxytocin concentrations were assayed for each subject. Oxy tocin was measured by RIA. We found no significant differences in plasma ox ytocin concentrations of individual subjects before and after intrathecal i njection, In addition, there were no significant differences in plasma oxyt ocin concentrations between the two groups when pooled samples from the sub jects were compared for the pre- and post-intrathecal injection phases. We conclude that the spinal intrathecal administration of fentanyl does not su ppress oxytocin secretion in pregnant women who are not in labour at term.