WARNING: SERIOUS AND LIFE-THREATENING RISKS FROM USE OF ALFENTANIL INJECTIONAddiction, Abuse, and MisuseALFENTANIL INJECTION exposes users to the risks of opioid addiction, abuse, and misuse, which can lead to overdose and death. Assess each patient’s risk prior to prescribing ALFENTANIL INJECTION and reassess all patients regularly for the development of these behaviors and conditions [see Warnings and Precautions (5.1)].Life-Threatening Respiratory DepressionSerious, life-threatening, or fatal respiratory depression may occur with use of ALFENTANIL INJECTION, especially during initiation or following a dosage increase. To reduce the risk of respiratory depression, proper dosing and titration of ALFENTANIL INJECTION are essential [see Warnings and Precautions (5.2)].Risks From Concomitant Use With Benzodiazepines Or Other CNS Depressants Concomitant use of ALFENTANIL INJECTION with benzodiazepines and/or other central nervous system (CNS) depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death. Reserve concomitant prescribing of ALFENTANIL INJECTION and benzodiazepines or other CNS depressants for use in patients for whom alternative treatment options are inadequate [see Warnings and Precautions (5.3), Drug Interactions (7)].Cytochrome P450 3A4 InteractionThe concomitant use of ALFENTANIL INJECTION with all cytochrome P450 3A4 inhibitors may result in an increase in alfentanil plasma concentrations, which could increase or prolong adverse reactions and may cause potentially fatal respiratory depression. In addition, discontinuation of a concomitantly used cytochrome P450 3A4 inducer may result in an increase in alfentanil plasma concentration. Monitor patients receiving ALFENTANIL INJECTION and any CYP3A4 inhibitor or inducer [see Warnings and Precautions (5.4), Drug Interactions (7), Clinical Pharmacology (12.3)].