Dipyrone is one of the most commonly used non-opioid analgesic and antipyretic drug. Its anti-nociceptive and hypothermic effects have long been suspected to be centrally mediated. The involvement of the most recently discovered opioid peptide, nociceptin/orphanin FQ (N/OFQ), and its receptor (NOP) in pain transmission is controversial. It appears to be pro-nociceptive when administered supra-spinally, but exerts anti-nociceptive effects when injected spinally or systemically.

Investigation of the role of the N/OFQ system in paracetamol-induced anti-nociception and hypothermia led us to determine its role in the anti-nociceptive and hypothermic effects of dipyrone.

Hot-plate and tail-flick tests were used to assess nociception, and a rectal thermometer was used to measure rectal temperature in mice.

Mice injected with dipyrone (150, 300, 600 mg/kg, i.p.) displayed dose-related anti-nociception and hypothermia. The NOP receptor antagonist JTC-801 (3 mg/kg, i.p.), at a dose that exerted no effect when used alone, alleviated dipyrone-induced anti-nociception but did not reverse dipyrone-induced hypothermia.

We conclude that NOP receptors participate in the anti-nociceptive, but not in the hypothermic, effects of dipyrone.

We compared the efficacy of intravenous lornoxicam vs. dipyrone in patient-controlled analgesia for postoperative analgesia.

The study included 105 patients who had undergone elective septorhinoplasty after receiving general anaesthesia. Patients were divided into three groups to receive lornoxicam (24 mg day−1), dipyrone (5 g day−1) or placebo. Pain was evaluated using a 0–100 mm visual analogue scale at 2, 4, 6, 8, 12, 16, 20 and 24 h postoperatively. Pethidine (1 mg kg−1) was administered intramuscularly to patients requiring rescue analgesia. Pethidine requirements were recorded during the first 24 h postoperatively, and treatment-related adverse effects were noted.

Postoperative pain scores were significantly lower with lornoxicam compared with dipyrone at 8 h (P = 0.016). No significant differences regarding pain scores at 2, 4, 6, 12, 16, 20 and 24 h were found. Significantly fewer patients in the lornoxicam group required rescue analgesics (vs. dipyrone, P = 0.046; vs. placebo, P = 0.001); fewer patients in the dipyrone group required rescue analgesics compared with placebo (P = 0.008). Significantly fewer patients in the lornoxicam group had nausea (vs. dipyrone, P = 0.022; vs. placebo, P = 0.006); no significant differences were found between the other two groups. Antiemetic use was significantly lower in the lornoxicam group (vs. dipyrone, P = 0.002; vs. placebo, P = 0.001).

Lornoxicam has better tolerability and is a more effective analgesic than dipyrone when administered by patient-controlled analgesia for postoperative analgesia after septorhinoplasty.