A group of 24 healthy parturients having elective cesarean section under epidural anesthesia with lidocaine with epinephrine were randomly divided into 2 groups. All patients simultaneously received an IM dose of 1 ml of solution and a 10 ml bolus via the epidural catheter. The coded ampules employed contained solutions prepared so that 11 patients received IM saline and 5 mg of morphine in 10 ml of solution epidurally, while 13 patients received 10 ml of epidural saline and 5 mg of IM morphine. Following drug injection at patient request, all patients were continuously monitored by pulse oximetry and respiratory inductive plethysmography so that respiratory rate and any apneic episodes were noted. Other observations were made of blood pressure, somnolence, pain, and presence of nausea, vomiting or pruritus. Side effects were treated as requested by diphenhydramine, dimenhydrinate and/or naloxone.