Is naloxone less effective when fentanyl is mixed with nonopioid drugs?

The overdose treatment naloxone is less effective in cases where fentanyl has been mixed with nonopioid drugs.

Naloxone, commonly sold as the nasal spray Narcan, works by reversing the effects of opioids, including fentanyl and heroin; it does not reverse the effects of other drugs, such as stimulants and nonopioid sedatives.

The federal Substance Abuse and Mental Health Services Administration says naloxone can still reverse the opioid part of an overdose, but it does not treat the effects of drugs such as benzodiazepines, cocaine or amphetamines.

The same applies to xylazine and medetomidine, nonopioid sedatives sometimes found in illicit drugs. The U.S. Centers for Disease Control and Prevention says naloxone should still be given in any suspected overdose, but it won’t reverse those drugs’ effects.

Portland police warned the community April 26 after seven suspected overdoses in less than 20 hours, urging people to call 911 and administer naloxone.