A comparison of regularly administered sustained release oral morphine with intramuscular morphine for control of postoperative pain

We studied the efficacy and side effect profile of regularly administered, oral sustained-release morphine sulfate tablets (MST) and IM morphine in patients undergoing total hip arthroplasty under lumbar spinal anesthesia. Patients in Group I received MST 20 mg 12 hourly and a placebo IM injection 6 hourly regularly. Group II patients received an oral placebo 12 hourly and morphine sulfate 10 mg IM 6 hourly regularly. Rescue analgesia was provided with regular diclofenac suppositories and patient-controlled analgesia. Pain scores assessed by using visual analog scale and verbal pain scoring at rest and with movement were low in both groups, with no statistical difference between groups. Mean patient-controlled analgesia morphine consumption during the 48-h study was 16.7 mg in the IM group and 25.9 mg in the MST group. The difference between the groups was significant at 36 h postoperatively (0.03). Side effects of sedation and respiratory depression were not problematic in either group, with a maximal sedation score of 2 occurring once in a patient in Group II. Nausea and vomiting occurred more often in Group II, but this was not statistically significant, with a mean nausea/vomiting score for Group II of 1.7. We conclude that oral, sustained-release morphine is an attractive alternative to LM opiates in patients undergoing body surface surgery under regional anesthesia. Implications: Each postoperative analgesic has its own limitations for route of administration, dosage, and potential side effects. Using the oral route for drug administration seems more attractive than other methods but may not be suitable in all postoperative patients. We studied the efficacy and side effect profile of sustained-release, oral morphine compared with standard IM morphine for the treatment of pain after hip replacement surgery. We concluded that use of the oral preparation is a suitable alternative to the IM route in this population undergoing surgery under spinal anesthesia.