Background: Postoperative pain relief after major surgery cannot be achieved with opioids alone in all patients without respiratory depression or other significant drawbacks. Modern medical practice, therefore, dictates the use of alternative analgesic agents as an adjunct or substitute to minimize the deleterious effects and to facilitate an earlier return to work and daily activities. Diclofenac and metamizol inhibit prostaglandin synthesis, thus attenuate the peripheral nociceptive sensitization caused by the surgical trauma. This investigation was conducted to determine the potency of diclofenac compared with metamizol in the control of postoperative pain after various plastic surgical operations under general anesthesia. Methods: A multiple-dose, randomized, double-blind clinical trial composed of one hundred and sixty-six patients was conducted. Group M patients received 1 g intramuscular metamizol (every 8 hours) and Group D patients received 75 mg intramuscular diclofenac (every 12 hours). Additional analgesia requirements were recorded and meperidine was used as the complementary analgesic when needed. Pain was assessed by visual analogue scores. Platelet count and bleeding time analyses were performed preoperatively and on the first postoperative day. Results: Metamizol decreased the additional analgesia requirement during the 18 hours following surgery. This was also associated with significantly lower pain scores. There was no significant difference between the patients receiving either metamizol or diclofenac in terms of pain scores, additional request for analgesia and frequency of side effects from the 18 th until the 48 th hour postoperatively. However, the use of diclofenac was associated with reduced side effects, though a reduction in platelet number and prolongation of bleeding time was noted in the majority of the patients receiving diclofenac. Conclusions: Metamizol is significantly superior to diclofenac for the reduction of postoperative pain after plastic surgery in the first 18 hours after plastic surgery procedures and reduces the need for additional analgesia.

        Key words: postoperative analgesia, diclofenac, metamizol