A 68-year-old man with a 10-year history of Parkinson's disease presents to the neurology clinic with worsening tremor and rigidity despite optimal levodopa therapy. His wife reports he has become increasingly forgetful over the past 6 months and occasionally becomes confused in the evenings. On examination, he has a resting tremor, cogwheel rigidity, and postural instability. His cognitive mini-cog score is 2/3. The neurologist decides to add an anticholinergic agent to his regimen. Which of the following anticholinergic drugs is MOST appropriate for this patient, and why?