Tabriz University of Medical Sciences Journal of Research in Clinical Medicine 2717-0616 12 1 2024 01 01 Donepezil overdose and its atypical clinical presentations: A case report 2 2 10.34172/jrcm.2024.32207 EN Mohammad Delirrad https://orcid.org/0000-0002-4663-9550 Habib Ahmadi Nader Aghakhani https://orcid.org/0000-0003-4026-2112 Journal Article 10.34172/jrcm.2024.32207 2022 02 12 2023 02 23 Donepezil [Aricept®] is a centrally acting reversible acetylcholinesterase inhibitor. We are reporting an unusual case of a 49-year-old male patient with a history of gastric bypass surgery who mistakenly ingested 200 mg of donepezil. During the hospital stay, atypical presentations such as tachycardia, disorientation, mydriasis, and ophthalmic myoclonus were diagnosed. He had experienced convulsions several times and developed rhabdomyolysis. The patient gradually improved under supportive management and was discharged from the hospital after seven days. The authors hope that reporting this case will provide both context for clinicians to be aware of its overdose that may be presented by atypical manifestations or side effects, along with the main muscarinic anticholinergic presentations.