Which of the following is a common side effect of tricyclic antidepressants (TCAs)?

Dry mouth is a well-documented common side effect of tricyclic antidepressants (TCAs). TCAs exert their pharmacological effects primarily by inhibiting the reuptake of norepinephrine and serotonin, but they also have anticholinergic properties due to their blockade of muscarinic receptors. This anticholinergic activity often leads to a decrease in salivary gland secretion, resulting in the sensation of dry mouth.

In comparison, increased libido is not typically associated with TCAs; most often, these medications can lead to sexual side effects such as decreased libido. Weight loss is less common, as TCAs are more likely to cause weight gain due to their sedative effects and influence on metabolism and appetite. Blurred vision can occur, but it is not as frequent as dry mouth and is more of a result of the anticholinergic effects. Thus, dry mouth stands out as a frequent and recognizable side effect of tricyclic antidepressants.