Which of the following is a known side effect of amitriptyline?

Amitriptyline, a tricyclic antidepressant, is known for its anticholinergic properties, which are responsible for various side effects throughout the body. One of the most common side effects associated with this medication is dry mouth, also known as xerostomia. This occurs because the medication inhibits the action of acetylcholine, a neurotransmitter that stimulates saliva production.

Understanding how amitriptyline affects the body helps clarify why dry mouth is a significant side effect. As users of the medication experience decreased salivary secretion, they may find their mouth feels physically dry, which can be uncomfortable and may lead to complications such as dental issues if not managed properly.

The other options, although they may have various clinical implications, do not have the same established association with amitriptyline. For example, tinnitus is not commonly reported as a side effect of this medication, urinary frequency is more related to different classes of medications, and exophthalmos is generally associated with specific thyroid conditions and is not directly related to amitriptyline. Thus, dry mouth stands out as the well-documented side effect directly linked to the pharmacological action of amitriptyline.