Which drug is the best choice for a patient with Alzheimer disease needing treatment for overactive bladder?

Trospium is the most appropriate choice for a patient with Alzheimer’s disease who also requires treatment for overactive bladder due to its pharmacological profile, specifically its lower propensity to cross the blood-brain barrier. This characteristic is particularly important for individuals with Alzheimer's, as drugs that can penetrate the central nervous system may exacerbate cognitive impairment or cause confusion, common side effects in this patient population.

Trospium works as an anticholinergic agent that primarily acts peripherally on the bladder, hence minimizing the risk of central side effects often associated with other anticholinergic medications. In contrast, other options like darifenacin, solifenacin, and tolterodine may have varying degrees of central nervous system penetration or anticholinergic side effects that could be detrimental to cognitive function.

Choosing trospium therefore maximizes the therapeutic benefits for managing overactive bladder while also safeguarding against potential cognitive decline or exacerbation of Alzheimer's symptoms.