Imidafenacin

Imidafenacin binds to and antagonizes muscarinic M1 and M3 receptors with high affinity. It also antagonizes muscarinic M2 receptors but with lower affinity. M3 receptors stimulate contraction of the detrusor muscle in the bladder via release of calcium from the sarcoplasmic reticulum. M2 receptors are also present in the detrusor muscle but serve to inhibit adenylate cyclase which reduces the relaxation mediated by β adrenergic receptors. Finally, M1 receptors are present on the parasympathetic neurons which release acetylcholine in the bladder. They act as an autocrine positive feedback loop and further increase release of acetylcholine. Antagonism of these receptors by imidafenacin prevents contraction of the bladder's detrusor muscle, prevents inhibition of the relation produced by sympathetic tone, and reduces acetylcholine release. Together these reduce the frequency of urination.