Examination of naloxone dosing patterns for opioid overdose by emergency medical services in Kentucky during increased fentanyl use from 2018 to 2021

Background: Fatal overdoses involving fentanyl/fentanyl analogs (F/FA) have increased in the US, raising questions about naloxone doses for F/FA overdose reversal. Emergency medical services (EMS) data provide an opportunity to examine naloxone administration changes as fentanyl increases in the illicit opioid supply. Methods: Administered naloxone intranasal-equivalent total dose (INTD) in milligrams (mg) was calculated for Kentucky EMS suspected opioid overdose (SOO) encounters (n=33,846), 2018–2021, and patterns of administration were examined. County-level F/FA availability was measured as 1) proportion of fatal drug overdoses involving F/FA, and 2) F/FA police seizures. Linear mixed models estimated changes in INTD in relation to local F/FA availability accounting for patient characteristics. Results: From 2018–2021, SOOs increased by 44% (6853 to 9888) with an average INTD increase from 4.5 mg to 4.7 mg, with more than 99% of encounters resulting in successful reversal each year. For SOO encounters examined by outcome at the scene (i.e., non-fatal fatal vs fatal), average INTD for non-fatal were 4.6 mg compared to 5.9 mg for fatal overdoses. Mixed modeling found no significant relationship between INTD and the two measures for local F/FA availability. Conclusion: As F/FA-involved overdose risk increased, we observed a modest increase in INTD administered in SOO EMS encounters – just slightly higher than the 4 mg standard dose. The lack of significant relationship between F/FA and naloxone dose suggests that naloxone utilization in SOO with EMS involvement remains effective for overdose reversal, and that EMS naloxone dosing patterns have not changed substantially.