Pharmacodynamic Evaluation of Intramuscular Nalmefene Autoinjector 1.5 mg Compared to Intranasal Narcan 4 mg

Key Inclusion Criteria include: 1. Healthy and free of significant abnormal findings as determined by medical history, physical examination, clinical laboratory values, vital signs, and ECG. 2. Body weight ranging from 50 to 100 kg (110-220 lbs) and body mass index (BMI) within the range \[18-30\] kg/m2 (inclusive). 3. Willing to be compliant with the protocol, capable of subjective evaluation, if applicable, able to read and understand questionnaires, if applicable. Key Exclusion Criteria include: 1. Females who are pregnant or lactating. 2. Any significant illness during the 30 days preceding the initial dose in this study. 3. History or any current conditions that might interfere with drug absorption, distribution, metabolism or excretion. 4. Refusal to abstain from caffeine or xanthine containing beverages entirely during confinement. 5. Refusal to abstain from consumption of alcoholic beverages 48 hours prior to initial study drug administration and through the end-of-study visit. 6. Difficulty with venous access or unsuitable for or unwilling to undergo catheter insertion. Other inclusion/exclusion criteria may apply.