## **Core Concept**
The question revolves around the acute retention of urine in a 60-year-old male with a history of depression, suggesting a drug-related cause. The core concept here involves understanding the side effects of various drugs used in treating depression, particularly those that can cause urinary retention.

## **Why the Correct Answer is Right**
The correct answer, **D. Amitriptyline**, is a tricyclic antidepressant (TCA). TCAs are known to have anticholinergic side effects, which include dry mouth, blurred vision, constipation, and importantly, urinary retention. This is because TCAs block the muscarinic acetylcholine receptors in the bladder, leading to decreased detrusor muscle contraction and thus, an inability to urinate.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Fluoxetine is an SSRI (Selective Serotonin Reuptake Inhibitor), which is less likely to cause urinary retention compared to TCAs. SSRIs can have various side effects but anticholinergic effects like urinary retention are rare.
- **Option B:** Mirtazapine is an atypical antidepressant with some anticholinergic properties but it is not as commonly associated with urinary retention as TCAs.
- **Option C:** Venlafaxine is an SNRI (Serotonin and Norepinephrine Reuptake Inhibitor), which has a different side effect profile that doesn't commonly include significant anticholinergic effects like urinary retention.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that tricyclic antidepressants (TCAs) like **Amitriptyline** have significant anticholinergic side effects, which can lead to urinary retention among other symptoms. This is a critical consideration in patients presenting with acute urinary retention and a history of depression.

## **Correct Answer:** D. Amitriptyline.