In addition to urinary retention, which other side effect could potentially be seen with trihexyphenidyl hydrochloride?

Trihexyphenidyl hydrochloride is an anticholinergic medication used primarily to treat extrapyramidal symptoms caused by antipsychotic medications, as well as for Parkinson's disease. One of the common side effects associated with anticholinergics is constipation. This effect occurs because the drug works by blocking the action of acetylcholine, a neurotransmitter that also plays a significant role in stimulating bowel motility. By inhibiting acetylcholine, trihexyphenidyl can lead to a decrease in gastrointestinal activity, resulting in constipation.

Other side effects of anticholinergics may include dry mouth, blurred vision, dizziness, and urinary retention, but in the context of the question regarding a significant side effect alongside urinary retention, constipation is particularly noted. This connection is crucial for understanding the medication's impact on the autonomic nervous system and the gastrointestinal tract.