Randomized placebo-controlled trial on local applications of opioids after hemorrhoidectomy.

BACKGROUND: Hemorrhoidectomy is associated with considerable postoperative pain. This study assessed whether a small dose of morphine or oxycodone administered in the embedded sponge set in the anus at the end of a hemorrhoidectomy intervention reduced postoperative pain. METHODS: The presence of opioid receptors was assessed in the anal mucosa excised from ten patients with perianal condyloma acuminata and 19 patients with symptomatic third-fourth degree hemorrhoids. A double-blind prospective randomized placebo-controlled trial was then conducted in 135 patients with hemorrhoids. Hemorrhoidectomy patients were randomized to morphine (MG), oxycodone (OG), or control (CG) groups, each patient having an absorbable sponge dressing left in the anus embedded with 1 mg of morphine, 1 mg oxycodone, or vehicle, respectively. The mean time for the first dose of analgesic drugs, the use of analgesics, and the mean time to void bladder was evaluated. RESULTS: The presence of kappa- and delta-opioid receptor immunoreactivity was detected in the anal mucosa excised from patients with perianal condyloma acuminata and hemorrhoids. Furthermore, there was a significant (P < 0.001) upregulation of kappa receptor immunoreactive-like material in hemorrhoidectomy patients. The mean time for the first analgesic administration was significantly increased (P < 0.001) in MG versus CG. A further significant increase (P < 0.001) was observed in the OG patient group. The mean time for voiding was significantly higher in CG when compared to the MG and OG patient groups. CONCLUSION: The local administration of very low doses of kappa-opioid agonist decreased hemorrhoidectomy postoperative pain through the interaction with specific opioid receptors located on anal mucosa.