What is a common side effect associated with TCAs?

Tricyclic antidepressants (TCAs) are known to have a variety of side effects due to their mechanism of action, which involves not only the reuptake inhibition of serotonin and norepinephrine but also significant interaction with various receptor types, including muscarinic acetylcholine receptors.

The common side effect of muscarinic blockade results from the anticholinergic activity of TCAs. This blockade interferes with the action of acetylcholine, leading to symptoms such as dry mouth, constipation, urinary retention, and blurred vision. These occur because the normal actions of acetylcholine on the parasympathetic nervous system are inhibited, which can significantly impact bodily functions.

D. Dry mouth, while a consequence of muscarinic blockade, is more of a specific symptom rather than the class effect itself. Weight gain and hypertension can occur with TCAs but are not as directly linked to their anticholinergic effects as muscarinic blockade is. This highlights how muscarinic blockade is a hallmark characteristic of the pharmacological actions of this class of medications.