Which of the following antispasmodics are NOT as selective for M3 receptors?

The choice of Oxybutynin and Fesoterodine reflects a key detail about their receptor selectivity. These medications, while being anticholinergic agents designed to alleviate conditions like overactive bladder, are recognized for their less selective targeting of M3 receptors compared to other available options. M3 receptors primarily mediate contraction of smooth muscle, particularly in the urinary bladder, which is crucial for the intended therapeutic effect.

Oxybutynin, in particular, has a broader action and also affects M1 and M2 receptors, leading to less predictability in terms of side effects. Fesoterodine, although intended to be more selective than older drugs, still displays variability in receptor affinity, meaning they engage with non-M3 receptor subtypes to some extent. This non-selectivity contributes to a wider array of therapeutic effects but may also lead to increased side effects.

In contrast, medications like Darifenacin and Solifenacin are specifically designed to have a higher selectivity for M3 receptors, aiming to reduce side effects associated with M1 and M2 influence, enhancing their therapeutic profile for bladder dysfunction. Similarly, Tolterodine and the combination of Trihexyphenidyl and Benztropine are noted for