Which of the following is a common side effect of anticholinergic agents?

Anticholinergic agents are known to block the action of acetylcholine, a neurotransmitter in the body that plays a key role in the functioning of the parasympathetic nervous system. One of the most commonly recognized side effects of anticholinergic medications is dry mouth, also known as xerostomia. This occurs because acetylcholine is responsible for stimulating the salivary glands; by inhibiting its action, anticholinergic agents reduce saliva production, leading to a sensation of dryness in the mouth.

In contrast, the other choices do not typically align with the effects of anticholinergic agents. Excessive sweating is generally associated with reduced sympathetic nervous activity or other causes rather than anticholinergic effects. Diarrhea and increased gastric motility are linked to increased secretions and muscular contractions in the gastrointestinal tract, which are not facilitated by anticholinergic activity. Instead, anticholinergic agents tend to slow down gastrointestinal motility and can lead to constipation. Therefore, the association of dry mouth with anticholinergic agents highlights a well-established side effect directly related to their mechanism of action in the body.