What is a common anticholinergic side effect of TCAs?

Anticholinergic side effects are commonly associated with tricyclic antidepressants (TCAs) due to their mechanism of action, which involves blocking the acetylcholine receptors in the body. One of the well-known anticholinergic effects is constipation. This occurs because acetylcholine plays a significant role in stimulating bowel motility; when its action is blocked, the smooth muscle contraction responsible for moving the contents through the gastrointestinal tract is diminished, leading to slower transit times and potential constipation.

In contrast, diarrhea is typically associated with increased motility rather than a reduction. Excessive sweating is not primarily an anticholinergic effect; rather, TCAs may sometimes cause decreased sweating due to anticholinergic properties, leading to a dry mouth and potentially increased body temperature. Weight loss is also not a direct anticholinergic effect, as TCAs can lead to weight gain in some patients due to their sedative properties and potential effects on metabolism. Therefore, constipation accurately reflects a common anticholinergic side effect experienced by patients taking tricyclic antidepressants.