Postoperative analgesia with controlled-release morphine sulphate: comparison with intramuscular morphine.

Fifty patients undergoing hysterectomy or cholecystectomy took part in a trail of postoperative analgesia provided by either intramuscular morphine or controlled-release morphine sulphate tablets orally. Respiratory function and plasma catecholamine concentrations were measured after operation and pain was assessed by using a linear analogue scoring method. Controlled-release morphine sulphate produced comparable pain relief with that of intramuscular morphine, and depression of respiratory function after operation was similar with the two analgesic regimens. The mean total dose of drug per patient given over 48 h to patients undergoing hysterectomy was 115 mg for morphine sulphate and 53 mg for morphine. Patients undergoing cholecystectomy received 130 mg morphine sulphate or 76 mg morphine. There was more sedation after operation in those patients undergoing hysterectomy who received morphine sulphate tablets. Morphine sulphate tablets produced satisfactory postoperative analgesia compared with intramuscular morphine: both regimens were acceptable to the patients.