Opioid toxicity

Opioid toxicity can occur when there is accumulation of opioid in a patient which may be due to new doses in an opioid naive patient, changes in drug metabolism due to deteriorating renal or hepatic function, incompatibility with a specific opioid or rapid dose escalation. Patients in their final weeks of life may be thought to be deteriorating or entering their final days due to the effects of opioid toxicity and it is important to exclude this as a reversible cause of a change in condition. However overzealous treatment may lead to poorly controlled pain, so must be assessed and balanced carefully.

Signs

• Respiratory depression
• Myoclonus
• Hallucinations
• Delirium
• Excess sedation

Management

• Check renal and liver function and correct if able
• Withhold culprit medication, and remove opioid patches
• Ensure prn doses remain available at half previous dose
• Supportive care such as supplemental oxygen and IV fluids should be considered if dehydrated, reduced oral intake, and felt to be appropriate
• Avoid reversal with naloxone unless RR<8 and oxygen saturations compromised as this will also reverse analgesia causing sudden, severe pain
• Consider opioid switch or restarting at half previous dose once symptoms improve