The doctoral dissertation of Panu Piirainen, Licentiate of Medicine, showed that oxycodone, a commonly used opioid, is feasible for epidural analgesia.
Epidural analgesia is effective in acute pain management after major surgery. Dilute local anaesthetics, opioid analgesics and epinephrine exert their analgesic effects in the spinal cord when administered into the epidural space. The epidural catheter tip is placed into the epidural space at a level that receives nociceptive input from surgical wound. For example, in lower abdominal surgery, the catheter is placed in the low thoracic- or high lumbar interspaces.
In his doctoral dissertation, Piirainen studied the analgesic efficacy of epidural oxycodone in patients undergoing gynaecological surgery. In Finland, oxycodone has been the most commonly used opioid in acute postoperative analgesia since the 1960s. However, the data on epidural administration are scarce.
In a randomised double-blind clinical trial in women undergoing gynaecological surgery, a single bolus of oxycodone was administered either epidurally or intravenously. Epidural oxycodone was more efficacious than the same dose delivered intravenously. Pruritus was more common in the epidural-group; but otherwise epidural oxycodone was well tolerated.
According to Piirainen, these results show that oxycodone is a feasible opioid for epidural analgesia as a part of multimodal analgesic regimen. A single bolus dose of oxycodone appears insufficient for analgesia after oped abdominal surgery; therefore, it may be beneficial to administer repeated intermittent doses or a continuous infusion of oxycodone alone or with dilute local anaesthetics and epinephrine.
In his doctoral dissertation, Piirainen also studied oxycodone concentrations in blood and cerebrospinal fluid samples that were collected from surgical patients. Population pharmacokinetic modelling indicated that 60 percent of oxycodone initially enters into cerebrospinal fluid and 40 percent is absorbed into the systemic circulation. According to Piirainen, this finding supports the theory that oxycodone exerts its analgesic action mainly in the spinal cord after epidural administration. For assessing the appropriate dosing protocol for repeated intermittent doses or a continuous infusion of epidural oxycodone, the developed population pharmacokinetic model can act as a key component for future pharmacokinetic-pharmacodynamic modelling.
Piirainen concludes that oxycodone is a feasible opioid for epidural analgesia. Further research is needed on repeated intermittent doses, continuous infusion and coadministering epidural oxycodone with dilute local anaesthetics.
The doctoral dissertation of Panu Piirainen, Licentiate of Medicine, entitled Pharmacokinetics and efficacy of epidural oxycodone will be examined at the Faculty of Health Sciences. The Opponent in the public examination will be Professor Teijo Saari of the University of Turku, and the Custos will be Docent Hannu Kokki of the University of Eastern Finland. The public examination will be held in Finnish on 20 August 2021 starting at 1 PM.
