Efficacy of postoperative analgesia with duloxetine in posthemorrhoidectomy pain: a prospective, randomized, double-blind and placebo-controlled trial

BACKGROUND: To evaluate the effect of duloxetine when added to a multimodal analgesia regimen on posthemorrhoidectomy pain, opioid consumption, and side effects. METHODS: Prospective, randomized, double-blind placebo-controlled trial. This study included 62 patients who underwent hemorrhoidectomy. The patients were randomly assigned to receive oral duloxetine 60 mg or placebo 2 h before and 24 h after surgery. The primary outcomes were pain intensity - measured on an 11-point visual analog pain scale - and cumulative morphine consumption at 12, 24, and 48 postoperative hours. RESULTS: Fifty-two patients completed the study (25 in the duloxetine group and 27 in the placebo group). Pain scores did not differ between duloxetine and placebo: 4.5; 3.0 – 7.0 vs. 5.0; 3.5 – 7.0, p = 0.68 at 12 h, 3.0; 2.0 – 5.0 vs. 3.0; 2.0 – 5.0, p = 0.56 at 24 h, and 2.5; 1.75 – 3.75 vs. 1.5; 0.5 – 3, p = 0.08 at 48 h. Further, cumulative morphine consumption did not differ between the duloxetine and placebo groups: 4; 1.25 – 10.75 mg vs. 7; 1.0 – 12.0 mg, p = 0.68 at 12 h, 9.5; 2.0 – 17.5 mg vs. 8.0; 4.0 – 18.0 mg; p = 0.80 at 24 h, and 11.0; 2.0 – 27.0 mg vs. 10; 4.0 – 24.0 mg, p = 0.78 at 48 h. Side effects did not differ between the groups. CONCLUSIONS: Compared with placebo, duloxetine did not decrease pain intensity or morphine consumption during the first 48 h postoperatively. TRIAL REGISTRATION: The study was retrospectively registered on the Brazilian Clinical Trials Registry (identifier: RBR-9pdgms, registration date: 08/10/2020).