What is a common anticholinergic side effect of TCAs?

Anticholinergic side effects are a well-known aspect of tricyclic antidepressants (TCAs). Blurred vision is one of the common effects that arise from the anticholinergic activity of these medications. This can occur due to the drug's influence on the eye's ability to accommodate, which is controlled by the ciliary muscle. Anticholinergic agents inhibit the action of acetylcholine, a neurotransmitter that plays a vital role in the contraction of the ciliary muscle, leading to difficulty in focusing on near objects, resulting in blurred vision.

While other options such as increased saliva production, decreased appetite, and increased energy might relate to other drug effects or conditions, they are not representative of anticholinergic effects. Increased saliva production, for instance, would typically be associated with substances that stimulate rather than inhibit cholinergic activity. Decreased appetite does not directly link to anticholinergic side effects, as these drugs may sometimes do the opposite, and increased energy is often more associated with stimulants rather than the sedative effects of TCAs. Therefore, blurred vision appropriately characterizes a common anticholinergic side effect experienced by patients taking tricyclic antidepressants.