Pharmacokinetic Properties of an FDA-approved Intranasal Nalmefene Formulation for the Treatment of Opioid Overdose

Nalmefene is a high-affinity, long-duration opioid antagonist that was approved in 1995 as an injection for the treatment of opiate overdose, but subsequently withdrawn (2008) for reasons other than safety or effectiveness. The dramatic rise in opioid overdose deaths over the past 7-8 years catalyzed the development of an intranasal (IN) formulation of nalmefene for the emergency treatment of opioid overdose. The studies described here compare the pharmacokinetic properties and safety profiles of an IN formulation containing nalmefene (2.7 mg in 0.1 mL) to an approved 1 mg intramuscular (IM) dose. IN nalmefene produced maximum plasma concentrations that were significantly higher than observed following the IM dose (12.2 and 1.77 ng/mL, respectively). The time to reach maximum plasma concentrations was also faster following IN administration (0.25 and 0.33 hours, respectively) with significant differences in plasma concentrations manifested as early as 2.5 minutes after administration (NCT04759768). The plasma half-life of nalmefene was similar following IM and IN administration (10.6-11.4 hours). Furthermore, dose-normalized nalmefene exposure was similar for both 1 spray in each nostril and 2 sprays in the same nostril compared to a single spray in each nostril (NCT05219669). There were no sex differences in the pharmacokinetic properties of either IN or IM nalmefene. In an era when almost 90% of opioid overdose deaths have been linked to high-potency synthetic opioids, the ability to rapidly deliver high concentrations of nalmefene could represent an important tool for reducing both morbidity and mortality.