Functional anticholinergic activity of drugs classified as strong and moderate on the anticholinergic burden scale on bladder and ileum

Several medications are commonly administered to older Japanese patients. Since some of them have not been included in previously developed scales to estimate the anticholinergic burden, we have developed a new muscarinic receptor binding-based anticholinergic burden scale. This study aimed to investigate the functional inhibitory effects of 60 medications, classified as anticholinergic burden scales 3 and 2 by the anticholinergic burden scale, on muscarinic receptor-mediated contractions in the bladder and ileum. The relaxation response induced by these drugs on isolated rat bladders and ileum smooth muscles constricted by carbachol was assessed using the organ bath method. All drugs inhibited smooth muscle contractile responses induced by the muscarinic receptor activation in a concentration-dependent manner in the rat bladder and ileum. Notably, variations were observed in the relaxation responses of the drugs, and the function EC₅₀ values were positively correlated with the binding IC₅₀ values in the bladder and ileum. The results of this study provide functional pharmacological evidence for the muscarinic receptor binding-based anticholinergic burden scale. Implementation of this scale may help reduce the risk of constipation and urinary retention, which are common side effects associated with anticholinergic drugs.