Intrathecal administration of morphine for the relief of pains in labour and estimation of maternal and fetal plasma concentration of morphine.

Thirteen healthy women in active labour received an intrathecal injection of morphine 1.0 mg. Eighty-five percent (11 patients) experienced acceptable or good pain relief. Analgesia set in 15-45 min after injection and reached a maximum after 15-120 min and lasted until delivery. Eighty-five percent (11 patients) of the patients developed mild side-effects i.e., pruritus, nausea and emesis. The intrathecal injection of morphine did not adversely affect the condition of the infant. Venous blood samples from the patients and umbilical cords for estimation of plasma morphine showed extremely low concentrations. No patients experienced any discomfort during the injection of morphine. These results indicate that morphine 1.0 mg administered intrathecally decreases labour pains to an acceptable level.