Background: The aim of the present study was to evaluate the efficacy of cholestyramine ointment (15 %) in reducing postoperative pain at rest and during defecation after open hemorrhoidectomy.

Methods: A total of 91 patients with third and fourth degree hemorrhoids undergoing open hemorrhoidectomy were included in this prospective, double-blind, randomized controlled trial. The patients were randomly assigned to either cholestyramine ointment or placebo immediately after surgery, 12 h after surgery, and then every 8 h for 14 days. The primary outcomes were intensity of pain at rest and during defecation, measured with a visual analog scale, and the analgesic requirement, measured by amount of tramadol consumption.

Results: The cholestyramine group had less postoperative pain than the placebo group at the 24th hour (1.84 ± 2.54 vs. 4.07 ± 3.35; P = 0.001) and 48th hour (0.18 ± 0.88 vs. 3.57 ± 3.45; P < 0.001) and less pain during defecation starting at the 48th hour (2.28 ± 2.96 vs. 4.77 ± 4.09; P = 0.001). Similarly, the average tramadol consumption at hours 24 and 48 was significantly lower for the cholestyramine group (5.32 ± 21.45 vs. 43.18 ± 61.56 mg at 24 h, and 4.48 ± 16.65 vs. 57.63 ± 65.47 mg at 48 h; P < 0.001). The only adverse event was pruritus, which had a lower frequency in the cholestyramine group but the difference was not significant until postoperative week 4 (P < 0.001).

Conclusions: Compared with placebo, cholestyramine ointment (15%) reduced postoperative pain at rest and on defecation, and consequently lowered the analgesic requirement after open hemorrhoidectomy.