Background Oxycodone/naloxone has a reported equivalent analgesic effect to oxycodone due to insufficient naloxone reaching systemic circulation to affect analgesia. Naloxone plasma concentrations can increase in some, e.g. patients with hepatic or renal impairment.
Case presentation A 75 year-old male with prostate and lung carcinoma was admitted for palliative radiotherapy. Admission analgesia included oxycodone/naloxone 70/35 mg bd, pregabalin 100 mg bd and oxynorm 20 mg prn.
Management Day 3: Multiple breakthroughs required for severe pain. Oxycodone/naloxone changed to oxycodone 90 mg bd (maximum licensed dose of oxycodone/naloxone exceeded). Pregabalin increased to 150 mg bd.
Day 4: Respiratory infection diagnosed and treated with intravenous antibiotics. Mild myoclonus but no other signs of toxicity. Pain ongoing.
Day 5: Sudden deterioration with respiratory depression (respiratory rate - 6, oxygen saturations -60%). Rapid response to naloxone 40micrograms intravenously. Opioids and pregabalin discontinued. Multiple further naloxone doses required for recurrent respiratory depression. Continuous subcutaneous infusion (CSCI) of 1.5 mg naloxone commenced.
Day 6: Naloxone infusion discontinued when pain recurred. CSCI of oxycodone 30mg/24hours commenced and subsequently rotated to hydromorphone 4mg/24hours due to mild opioid toxicity.
Radiotherapy completed and patient discharged home on hydromorphone and gabapentin.
Discussion Given the timing, and despite normal renal and liver function, we believe the oxycodone/naloxone to oxycodone switch contributed to the severity of opioid toxicity in this case. Other possible factors include infection and titration of pregabalin.
When repeated naloxone doses are required for toxicity, a continuous intravenous infusion often necessitates transfer to an acute hospital and may be avoided by administering a CSCI of naloxone. To the best of the authors’ knowledge, this is the first case report of naloxone administered via CSCI for opioid toxicity.
Conclusion When switching preparations of oxycodone, specific patient factors and intra- and inter-patient variability should be considered and patients monitored carefully. CSCIs of naloxone for opioid toxicity should be considered if intravenous administration is not feasible.
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