The overdose epidemic has accounted for nearly 1 million lives lost in the United States in the past 2 decades.1 Although the majority of overdose deaths are opioid related, the type of opioid involved and corresponding mortality rates vary over time, with fentanyl presently driving the fatality count in opioid- and stimulantinvolved overdose deaths alike. Emergency medical services (EMS) are typically deployed in response to overdose and poisoning calls for service, and EMS administer naloxone (an opioid antagonist) when indicated to reverse respiratory depression caused by opioids.
Although there are substantial geographic and policy differences in who administers naloxone and under what circumstnaces,4 the number of EMS naloxone administrations per capita are increasingly used for public health surveillance purposes5 and to guide resource allocation.
However, the search continues to identify factors that reliably precede overdoses to trigger and inform targeted prevention efforts.7–9 We explored law enforcement drug market disruptions as a potential factor. People can develop a tolerance for opioids, although overdose occurs when dosage exceeds tolerance to the point of respiratory failure. Unknown opioid tolerance at relapse is a documented overdose risk factor among the recently incarcerated10,11 and those discharged from residential treatment and withdrawal management settings.12,13 Reductions in tolerance can occur after any involuntary disruption of an individual’s opioid supply, and accidentally ingesting a dose beyond one’s tolerance can be fatal.
This mechanism accounts for the second wave of the overdose epidemic, when consumers shifted from pharmaceutical opioids to heroin. Heroin is a much less consistent and predictable product, increasing the dangers that come of unknown tolerance, especially overdose risk.
