Further Insights Into Anticholinergic Action Informed by Japanese Anticholinergic Risk Scale

The increased anticholinergic burden caused by medications in older adults is one of the adverse drug reactions of particular concern, as it can exacerbate the onset of geriatric syndromes or induce cognitive dysfunction, and is also related to the issue of polypharmacy. One year has passed since the "Japanese Anticholinergic Risk Scale" was published by the Japanese Society of Geriatric Pharmacy, and the anticholinergic effects of various medications have garnered attention. These medications are used in clinical practice and research. The anticholinergic effects of drugs are not necessarily induced solely by binding to muscarinic receptors and exerting antagonistic actions but may also occur as a result of various combined effects. In this review, we focus on drugs that show differences between the "Yamada Classification," which was created based on in vitro muscarinic receptor binding activity, and the "Japanese Anticholinergic Risk Scale." We re-examine anticholinergic effects and, through a review of the literature, identify drugs that induce "anticholinergic-like effects" beyond direct muscarinic receptor antagonism. By understanding the potential mechanisms underlying "anticholinergic-like effects" in drugs where anticholinergic effects listed in the risk scale are not anticipated, we aim to reemphasize the prevalence of drugs with anticholinergic-like effects.