Patient-controlled analgesia versus oral controlled-release oxycodone - are they interchangeable for acute postoperative pain after laparoscopic colorectal surgeries?

BACKGROUND: Standard therapy for postoperative pain after laparoscopic colorectal surgeries at the Tan Tock Seng Hospital consists of intravenous morphine via patient-controlled analgesia (PCA) for the first 24-48 h, followed by oral analgesics. We compared the efficacy and safety of oral controlled-release (CR) oxycodone hydrochloride (OxyContin tablets) and PCA after laparoscopic colorectal surgeries.

METHODS: Between March and August 2006 (phase 1 study), 14 patients underwent laparoscopic colectomy, laparoscopic hemicolectomy or laparoscopic-assisted anterior resections. All patients were on oral CR oxycodone with oral immediate-release oxycodone on an as-needed basis for breakthrough pain. Pain intensity, analgesic use, length of hospital stay and side effects were evaluated. These were compared to data obtained from a second study of a similar design where 9 patients underwent similar operations from October 2006 to July 2007 (phase 2 study) and were on PCA morphine.

RESULTS: All patients in the CR oxycodone and PCA morphine groups needed the opioid medication for only 2 days. There was no difference in mean (range) postoperative pain intensity scores between patients on oxycodone and those on PCA morphine for the 1st postoperative day [2.07 (0-5) vs. 2.78 (2-4) on a Visual Analogue Scale (VAS) from 0 to 10; p = 0.10] and the 2nd postoperative day [1.14 (0-2) vs. 1.67 (0-3); p = 0.10]. Generalized estimating equations with linear link function confirmed that there was a significant relief of pain in patients after operation. On average, the VAS score of pain was 1.00 units lower on day 2 when compared with day 1 (p < 0.01). The mean (range) doses of oxycodone used on the 1st and 2nd postoperative day were 13.57 mg (10-30) and 15.36 mg (10-30), and the mean (range) doses of morphine used on the 1st and 2nd postoperative day were 14.9 mg (8-28) and 16.3 mg (4-31), respectively. Incidence of nausea and vomiting was 14.2 and 20% for the CR oxycodone and PCA groups, respectively.

CONCLUSIONS: Oral CR oxycodone 20 mg per day is a cheaper, convenient and an efficacious alternative analgesic to PCA opioids after laparoscopic colorectal surgery.