Impact of Preemptive Methadone or Paracetamol in Controlling Pain after Lower Abdomen Surgery under General Anesthesia

The aim of this study was to evaluate the effect of preemptive methadone or paracetamol on postoperative pain in lower abdomen surgery under general anesthesia in comparison with control group.
This was a randomized clinical trial study on 96 patients undergoing lower abdominal surgery. The subjects were divided into three groups. In the first group, 15 mg intravenous paracetamol was injected gradually after anesthesia induction and before surgery. In the second group, 0.15 mg/kg intramuscular methadone was injected into patient's deltoid muscle before anesthesia induction. In the third group, same volume of normal saline was injected. Then, pain intensity were evaluated in all three groups in recovery and ward up to 24 hours using visual analog scale (VAS).
Findings: Pain intensity at 30 minutes after the surgery in the paracetamol group with a mean of 0.73 ± 0.31 was significantly lower than methadone group with a mean of 2.53 ± 0.54; and in both groups received the drugs was significantly lower than control group with a mean of 2.97 ± 0.57 (P 0.050).
According our results, preemptive methadone had a much better effect in controlling postoperative pain compared to preemptive paracetamol; however, complications of paracetamol were less than methadone. Finally, pain intensity was evaluated equal in two groups for up to 24 hours after the surgery.