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The FDA approved the first nalmefene hydrochloride auto-injector (Zurnai) for use as an emergency treatment for opioid overdose in adults and children 12 years of age and older, the agency Wednesday.

Nalmefene is an opioid receptor antagonist used to treat acute opioid overdose, initially approved in 2022 as an for use by healthcare professionals and, since May 2023, as a nasal spray formulation (Opvee). If administered quickly, the treatment can reverse the effects of opioid overdose, such as respiratory depression, sedation, and hypotension.

The agency noted that nalmefene and naloxone (Narcan) are the only two available options to reverse opioid overdose. Naloxone is available as an intramuscular injection, intramuscular auto-injection, and nasal spray. The latter was approved last year for over-the-counter use.

While nalmefene is similar to naloxone, it has been shown to have longer-lasting effects, including a plasma half-life of roughly 11 hours compared with about 2 hours for naloxone. Perceived to be more potent than naloxone, some harm reduction groups have warned that nalmefene could bring symptoms.

The new injectable formulation of nalmefene contains a single 1.5-milligram dose in a pre-filled auto-injector, which is designed to be delivered either subcutaneously or intramuscularly. It will only be available with a prescription, according to the agency.

"The FDA remains focused on broadening access to opioid overdose reversal agents, including naloxone and nalmefene. Today's approval adds a new nalmefene product and route of administration to support greater options for opioid overdose reversal," FDA Commissioner Robert Califf, MD, said in an agency press release. "Since launching the in 2022, the agency continues to build upon efforts that address the overdose crisis currently impacting the nation."

The approval rested on safety and pharmacokinetic studies. Common adverse effects included dizziness, nausea, headache, and vomiting. The agency added that individuals treated with nalmefene may also experience opioid withdrawal symptoms, such as body aches, diarrhea, tachycardia, and fever.

Notably, Purdue Pharma is the maker of injectable nalmefene products. The pharmaceutical company, which was run by the Sackler family until 2019, was also the maker of the long-acting opioid oxycodone (OxyContin). Since that drug entered the market in 1996, it is widely considered to have played a significant role in the opioid epidemic. The company has been subject to several lawsuits over its role in that crisis, including a failed attempt to file for bankruptcy.

Purdue has sold nalmefene at cost, without making a profit, and to do so with the new formulation.

The agency granted the company's drug application Fast Track and Priority Review designations, which expedited the development and review of auto-injectable nalmefene, due to "the potential to provide a significant improvement in the safety or effectiveness of the treatment, diagnosis or prevention of a serious condition."

Drug overdose deaths continue to be a major public health issue across the country, with more than 107,000 fatal overdose deaths in 2023, primarily driven by synthetic opioids such as illicit fentanyl, FDA said.

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