Pentazocine, a Kappa-Opioid Agonist, Is Better Than Diclofenac for Analgesia in Acute Pancreatitis: A Randomized Controlled Trial

OBJECTIVES: The ideal analgesic is not known for patients with acute pancreatitis (AP). Concerns have been raised about serious adverse effects of opioid analgesics increasing the severity of AP. We hypothesized that nonsteroidal anti-inflammatory drugs might be better analgesics because of their anti-inflammatory effect. Our objective was to compare pentazocine, an opioid, and diclofenac, a nonsteroidal anti-inflammatory drug, for adequate analgesia in patients with AP. METHODS: In a double-blind randomized controlled trial, patients with AP were randomized to either intravenous diclofenac 75 mg or pentazocine 30 mg. Fentanyl was given as a rescue analgesic through a patient-controlled analgesia pump. Primary outcome was pain relief measured objectively by the dose of fentanyl required as the rescue analgesic, pain-free period, and numbers of effective and ineffective demands of fentanyl. Secondary outcome was adverse events. RESULTS: Fifty patients were randomized, 24 to the pentazocine group and 26 to the diclofenac group. Baseline characteristics were comparable between the groups. Pentazocine was found to be better than diclofenac in terms of significantly lower dose of the rescue analgesic (fentanyl) required (126 μg (interquartile range (IQR) 65–218 μg) vs 225.5 μg (IQR 133–427 μg); P = 0.028) and longer pain-free period (31.1 ± 8.2 vs 27.9 ± 6.6 hours, P = 0.047). The number of effective and ineffective demands was lower in the pentazocine group compared with the diclofenac group (11.5 (IQR 8–15) vs 16 (IQR 13–20), P = 0.098) although not statistically significant. Adverse events were similar between the groups. CONCLUSIONS: Pentazocine, a kappa-opioid receptor agonist, was significantly better than diclofenac for pain relief in AP (Trial registration number: CTRI/2016/09/007326).