On May 22, 2023, the United States Food and Drug Administration approved the first nalmefene hydrochloride nasal spray for the emergency treatment of known or suspected opioid overdose in adults and pediatric patients 12 years of age and older. This approval of a new prescription nalmefene hydrochloride nasal spray adds to the available opioid reversal options for hospitals, communities, harm reduction groups, and emergency responders. Due to the life-threatening nature of opioid overdose, conducting randomized, well-controlled clinical efficacy trials in the target patient population is neither ethical nor feasible. Clinical investigations of nalmefene nasal spray consisted of two pharmacokinetic studies and one pharmacodynamic study. Approval of the new drug application was based on the scientific bridge established by the two pharmacokinetic studies to the Agency's previous efficacy and safety findings for the listed drug nalmefene hydrochloride injection. Additionally, the pharmacodynamic study conducted in an opioid-induced respiratory depression model in healthy volunteers established the onset of action of nalmefene administered as a nasal spray. A high-level summary of regulatory and scientific considerations during the development and approval of nalmefene nasal spray are presented.