# Post-marketing Surveillance of Intranasal Nalmefene: Prevalence and Clinical Relevance of Precipitated Withdrawal

## TL;DR

A study using real-world data found that intranasal nalmefene rarely causes precipitated withdrawal, supporting its safe use for opioid overdose reversal.

## Contribution

This is the first post-marketing surveillance study to assess precipitated withdrawal risk with intranasal nalmefene.

## Key findings

- Only 2 out of 15 adverse event reports indicated precipitated withdrawal after nalmefene use.
- No severe or treatment-limiting withdrawal cases were observed in the study period.
- The overall signal strength for precipitated withdrawal was low, with no disproportionate reporting.

## Abstract

Background: Intranasal (IN) nalmefene (OPVEE®) was approved as an opioid overdose reversal agent with a pharmacological profile distinct from IN naloxone, raising early concerns about the potential for precipitated withdrawal despite the absence of evidence.

Objective: This study aimed to evaluate the prevalence and clinical significance of precipitated withdrawal following the administration of IN nalmefene using post-marketing surveillance data.

Methods: We conducted a comprehensive analysis of adverse event reports submitted to Indivior's Global Safety Database following the commercial launch of IN nalmefene in October 2023. Reports were screened for terms consistent with opioid withdrawal syndromes, and cases were assessed for temporal association, severity, and clinical outcomes.

Results: Through July 2025, there have been 246 confirmed reversals with IN nalmefene across the United States. Among the total adverse event reports received (n=15), instances of precipitated withdrawal were rare (n=2). Most reports lacked sufficient clinical details to confirm causality, and no consistent pattern of severe or treatment-limiting withdrawal emerged. The overall signal strength for precipitated withdrawal was low, with no indication of a disproportionate reporting trend.

Conclusions: Post-marketing surveillance data suggest that the risk of precipitated withdrawal with IN nalmefene is low in real-world settings. These findings support the continued deployment of IN nalmefene as a life-saving intervention while underscoring the importance of ongoing pharmacovigilance to monitor for emerging safety signals.