Benztropine

Muscarinic blockade reduces salivary secretion. Management: sugar-free gum, sips of water, saliva substitutes. Often the most bothersome daily side effect.

Muscarinic blockade reduces GI motility. Usually manageable with fiber and stool softeners. In combination with other anticholinergic medications (especially clozapine), constipation can progress to ileus, a medical emergency. Monitor bowel function in patients on multiple anticholinergics.

Muscarinic blockade affects detrusor muscle. Particularly concerning in elderly men with prostatic hypertrophy. Can present as hesitancy, incomplete voiding, or acute retention.

Muscarinic blockade causes mydriasis and cycloplegia (impaired accommodation). Difficulty with near vision is typical. Usually dose-dependent.

Central muscarinic blockade affects memory and attention. Often subtle and underrecognized. May be attributed to the psychiatric illness rather than the medication. Elderly patients are particularly vulnerable. This is the strongest reason to minimize long-term benztropine use.

Vagolytic effect (muscarinic blockade of cardiac vagal tone). Usually asymptomatic but may be distressing.

Some H1 antagonism and central anticholinergic effects contribute to drowsiness.

Anticholinergics impair sweating (thermoregulatory mechanism is muscarinic). Patients on benztropine are at increased risk of heat-related illness in hot environments. Counsel about heat exposure, hydration, and recognition of heat exhaustion symptoms.

Benztropine at supratherapeutic doses can produce euphoria and altered mental states. Misuse has been reported particularly in inpatient psychiatric and forensic settings. Monitor for dose escalation requests, lost medication claims, and diversion.