New Type of Opioid Reversal Agent Approved

The first nalmefene hydrochloride nasal spray (Opvee) won FDA approval for the emergency treatment of known or suspected opioid overdose in adults and pediatric patients 12 years of age and up, the agency announced.

If administered quickly, the opioid receptor antagonist provides fast onset and long duration reversal of opioid-induced respiratory depression. It will be available for use by prescription in healthcare and community settings.

"The agency continues to advance the FDA Overdose Prevention Framework and take actionable steps that encourage harm reduction by supporting the development of novel overdose reversal products," said FDA Commissioner Robert M. Califf, MD, in a statement. "On the heels of the FDA's recent approval of the first over-the-counter opioid reversal agent, the availability of nalmefene nasal spray places a new prescription opioid reversal option in the hands of communities, harm reduction groups, and emergency responders."

Nalmefene is similar to naloxone (Narcan) but longer-lasting to match the duration of action of most opioids, with a plasma half-life of about 11 hours compared with approximately 2 hours for naloxone. Each spray delivers a 2.7-mg dose of nalmefene into the nasal cavity.

Drug overdose continues to be a major public health issue in the U.S., with more than 105,000 reported fatal overdoses occurring in 2022, primarily driven by synthetic opioids such as fentanyl.

Approval of nalmefene was granted to Opiant Pharmaceuticals, which was recently acquired by Indivior.

"Despite our collective effort to stem opioid abuse in America, addiction can happen to anyone, and millions of people are at risk for not only opioid overdose, but also poisoning from illicit synthetic opioids such as fentanyl," said former U.S. Surgeon General Jerome Adams, MD, MPH, the executive director of health equity initiatives at Purdue University in West Lafayette, Indiana, in an Indivior press release.

Nalmefene's approval was supported by safety and pharmacokinetic studies. Study participants showed that the time to onset of reversal of respiratory depression was observed between 2.5 to 5 minutes and full recovery of respiratory drive was manifested as early as 5 minutes after nalmefene administration.

The most common adverse reactions include nasal discomfort, headache, nausea, dizziness, hot flush, vomiting, anxiety, fatigue, nasal congestion and throat irritation, pain in the nose, decreased appetite, skin redness, and excessive sweating.

Indivior warned that it is possible that nalmefene use is followed by a recurrence of respiratory depression, so recipients should be kept under continued surveillance and given repeat doses as necessary while awaiting emergency medical assistance. Larger or repeat doses of nalmefene may also be needed to completely reverse the effects of buprenorphine, pentazocine, and other partial agonists or mixed agonists/antagonists.

Additionally, recipients of the rescue medication should be monitored for the development of opioid withdrawal, which may be life-threatening in some cases.

The company said it expects to have nalmefene on the market in the last quarter of 2023.

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