Fentanyl, also spelled fentanil, is a powerful opioid used as a pain medication and, together with other medications, for anesthesia.[3] It is also used as a recreational drug, sometimes mixed with heroin, cocaine, benzodiazepine or methamphetamine. In 2020, fentanyl tablets containing xylazine (horse tranquilizer) began circulating.[5] Its potentially deadly overdose effects can be neutralized by naloxone.[6] Fentanyl is commonly used to create counterfeit pills disguised as OxyContin, Xanax, Adderall, among others. It has a rapid onset and its effects generally last under two hours.[3] Medically, it is used by injection, nasal spray, or skin patch, or absorbed through the cheek as a lozenge or tablet.[3][7]
Common side effects of fentanyl include nausea, vomiting, constipation, itching, sedation, confusion, and injuries related to poor coordination.[3][8] Serious side effects may include respiratory depression, hallucinations, serotonin syndrome, low blood pressure, or development of an opioid use disorder.[3][8] Fentanyl works primarily by activating μ-opioid receptors.[3] It is around 100 times stronger than morphine and about 50 times stronger than heroin. Some fentanyl analogues such as carfentanil are up to 10,000 times stronger than morphine.[9]
