Differential effect of opioids in patients with chronic pancreatitis: An experimental pain study

Objective. Animal experiments and clinical observations have indicated a different working profile of oxycodone compared to morphine, and it has previously been shown that oxycodone attenuates visceral pain better than morphine. The objective of this study was to test the effects of oxycodone and morphine on experimental pain in patients with pain caused by chronic pancreatitis. Material and methods. Ten patients took part in this blinded, cross-over study. The analgesic effects of morphine ( 30 mg, oral), oxycodone ( 15 mg, oral) and placebo were tested against multimodal ( mechanical, thermal and electrical) experimental pain in the skin, muscles and oesophagus. Pain was assessed at baseline and 30, 60 and 90 min after drug administration. Results. In the skin and muscles, oxycodone was more effective than placebo and morphine on mechanically ( skin: F = 12.4, p < 0.001, muscle: F = 11.0, p < 0.001) and thermally ( skin: F = 8.5, p < 0.001) evoked pain. In oesophageal heat pain, the effect of morphine was equal to that of placebo, while oxycodone attenuated pain better than both morphine and placebo ( F = 9.5, p < 0.001). Both morphine and oxycodone were more effective in attenuating mechanical pain in the oesophagus than placebo ( F = 8.6, p < 0.001). After electrical stimulation no differences were seen between the opioids and placebo in any tissue studied. Conclusions. Oxycodone was a stronger analgesic than morphine in several pain modalities in the skin, muscle and oesophagus.