Multicenter trial comparing tramadol and morphine for pain after abdominal surgery.

Seventy patients (40 male, 30 female), mean (SD) age 60.8 +/- 13.7 years were treated with parenteral morphine (10 mg/1 ml ampul) or tramadol (100 mg/2 ml ampul) to verify their analgesic effects in pain following abdominal surgery. The multicenter trial followed an open, controlled experimental design between patients, randomized within the centers. The drugs were given by intramuscular injection, as requested by patients, starting in the postoperative period when pain was more than 70 mm, assessed on a visual analog scale. Patients were allowed up to six ampuls of tramadol or morphine in the 24-h trial but in the first 4 h, if they asked for supplementary analgesic, only diclofenac (75 mg in a 3-ml ampul) was allowed. Both test drugs gave rapid and constant pain relief. After the first dose, pain intensity was reduced 36.2% with tramadol, and 51% with morphine; the pain-free interval was similar for both treatments. The quality of sleep and the number of hours of sleep the night after surgery were similar for both groups. Tramadol was tolerated better, giving rise to no untoward reactions; with morphine there was one case of mild respiratory depression. In abdominal surgery, therefore, tramadol given by intramuscular injection has postoperative analgesic activity similar to morphine, but is better tolerated.