Which side effect is commonly associated with the use of TCAs?

The side effect commonly associated with the use of tricyclic antidepressants (TCAs) is dry mouth. This occurs due to the anticholinergic effects of TCAs, which inhibit the action of acetylcholine, a neurotransmitter that helps to stimulate saliva production. Consequently, patients using TCAs may experience reduced salivary flow leading to a sensation of dryness in the mouth.

While other side effects can occur with TCAs, such as nausea and changes in sleep patterns, dry mouth is particularly prevalent due to the medication's mechanism of action. Hyperactivity is not typically associated with TCAs, as they often have a sedative effect, and insomnia is more frequently related to other types of medications or the condition being treated rather than TCAs themselves. Thus, dry mouth stands out as a classic side effect in the context of tricyclic antidepressants.