A 78-year-old woman is brought to the clinic by her daughter because she is concerned about her mother’s mood. The patient’s husband of 48 years passed away 6 months ago after a lengthy illness due to metastatic colon cancer. Since then she reports having a poor appetite, decreased interest in activities, and frequent thoughts about dying. She is started on nortriptyline to help improve her mood and functional status. Which of the following is the most common side effect of nortriptyline?

**Core Concept**
Nortriptyline is a tricyclic antidepressant (TCA) commonly used to treat major depressive disorder (MDD) and neuropathic pain. Its mechanism of action involves the inhibition of the reuptake of norepinephrine and serotonin, leading to increased levels of these neurotransmitters in the synaptic cleft and improved mood.

**Why the Correct Answer is Right**
The most common side effect of nortriptyline is **dry mouth**, also known as xerostomia. This occurs due to the anticholinergic effects of the medication, which block the action of acetylcholine at muscarinic receptors in the salivary glands. This leads to a reduction in salivary secretion, resulting in dry mouth. Other anticholinergic effects of nortriptyline include blurred vision, constipation, and urinary retention.

**Why Each Wrong Option is Incorrect**
**Option A:** Weight gain is a common side effect of many antidepressants, but it is not the most common side effect of nortriptyline. Weight gain is more commonly associated with selective serotonin reuptake inhibitors (SSRIs).

**Option B:** Sedation is a common side effect of many antidepressants, but it is not the most common side effect of nortriptyline. Sedation is more commonly associated with TCAs that have a higher affinity for histamine receptors, such as amitriptyline.

**Option C:** Confusion and disorientation are not common side effects of nortriptyline. These symptoms are more commonly associated with TCAs that have a higher affinity for muscarinic receptors, such as amitriptyline.

**Clinical Pearl / High-Yield Fact**
Anticholinergic side effects of TCAs, such as dry mouth and blurred vision, can be mitigated by using a low dose and gradually increasing it as needed. Patients should also be advised to drink plenty of water and use sugar-free gum or candy to stimulate saliva production.

**Correct Answer:** D. Dry mouth.

✓ Correct Answer: D. anticholinergic side effects