Abstract
Naltrexone is an μ opioid receptor antagonist that is used in alcohol and opiate use disorder. Naltrexone does not constitute tolerance and dependence, and cessation of the drug does not cause withdrawal symptoms. Sustained release form of naltrexone has been developed due to patient compliance issues. There is currently only one sustainedrelease form available in Turkey, which is inserted subcutaneously. In this case report, we present, a probable serious side effect of sustained release naltrexone implant. A 36 years old male with alcohol use disorder, developed a sudden clouding of consciousness one hour after the naltrexone implant application followed by anterograde amnesia in the next 8-10 hours. We were not able to detect any medical or neurological reasons for the altered mental status but after the removal of the naltrexone implant, the symptoms improved. To the best of our knowledge, this is the first case to report clouding of consciousness and anterograde amnesia after naltrexone implantation. Keywords: Naltrexone Implant, Side Effect, Alcohol Use Disorder, Lethargy, Consciousness.