Objective: To determine the frequency and potential predictors of opioid toxicity recurrence after a response to naloxone in adult Emergency Department patients.
Methods: A retrospective case-control study of naloxone-treated patients with opioid toxicity over an 8-year period. Both the patient response to naloxone and recurrence of opioid toxicity was determined by an expert Delphi Panel. The frequency of opioid toxicity recurrence was compared by the duration of opioid effect, the route of opioid exposure, and the presence of other CNS depressant drugs.
Results: Ninety of 221 (41%) cases with a discharge diagnosis of opioid toxicity were treated with naloxone; six patients were excluded because of a lack of toxicity. There was a response to naloxone in 50% of the 84 cases, and recurrence of toxicity in 31% (95% CI 17-45%) of naloxone responders. The most common opioids were codeine, heroin, propoxyphene, and oxycodone/hydrocodone. Recurrence of toxicity was more common with long-acting opioids (p = 0.04), and was not associated with the route of opioid exposure (p = 0.42), or presence of ethanol and other CNS depressants (p > or = 0.87).
Conclusion: Opioid toxicity recurrence after a response to naloxone occurred in approximately 1/3 of adult Emergency Department opioid overdose cases. Recurrence was more common with long-acting opioids and was not associated with the route of opioid exposure. Other clinically useful predictors of toxicity recurrence were not identified.