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Introduction The present study was attempted to evaluate the effect of perianal infiltration of tramadol on postoperative pain in patients undergoing hemorrhoidectomy. Method This double-blind clinical trial study was carried out on 90 patients with grade 3 and 4 hemorrhoids undergoing hemorrhoidectomy. Patients were randomly assigned into 3 groups of control or bupivacaine or tramadol. Before the surgery, perianal infiltration of .25% bupivacaine or tramadol or normal saline was prescribed to each group, respectively. Data on pain severity (based on the visual analog scale (VAS), the duration of surgery, sedation score, pain at the first defecation, first request time for additional analgesia, nausea and vomiting, and analgesic intakes) were evaluated and analyzed. Results Duration of surgery was almost similar in all 3 groups ( P = .974). The results showed a significant difference in pain score between 3 groups ( P ≤.05) at all times after the surgery. In addition, the means of sedation scores ( P = .03), pain score at the first defecation ( P = .001), the time to first analgesic request ( P = .001), and ketorolac administration times ( P = .01) were significantly different between 3 groups. Finally, no complication was reported regarding postoperative nausea and vomiting. Conclusion Given the notable efficacy of tramadol in reducing pain after hemorrhoidectomy and its minor side effects, this medication is suggested as an effective topical anesthetic to decrease pain after hemorrhoidectomy.

In our previous study, we reported that chronic morphine exposure changes neuronal response properties in rat somatosensory cortex. In this study, we investigated the effect of chronic morphine treatment on tactile learning behavior in rats. Morphine sulfate was dissolved in tap water, and was administered for 21 days. Tactile learning was assessed using the novel object recognition test (NORT) in a dark room. The chronic morphine treated group exhibited a learning impairment; the discrimination ratio was significantly lower as compared to the control group. These findings suggest that chronic exposure to morphine impaired the tactile learning in rats as the discrimination ratio was decreased following morphine administration.