**Core Concept:** Overactive bladder (OAB) is a clinical condition characterized by urinary urgency, usually accompanied by frequency and nocturia, with or without incontinence, in the absence of a more significant urological cause. OAB affects bladder detrusor muscle involuntary contractions.

**Why the Correct Answer is Right:**
Antimuscarinic drugs are commonly used to treat OAB. These drugs work by blocking the action of acetylcholine at the muscarinic receptors of the bladder wall. They reduce the detrusor muscle contractions and lower the bladder capacity, leading to decreased frequency and urgency of urinary urges.

**Why Each Wrong Option is Incorrect:**
A. This option is incorrect because it is a different class of medication, targeting different receptors (e.g., alpha-blockers for benign prostatic hyperplasia).
B. This option is incorrect because it is also a different class of medication, targeting different receptors (e.g., beta-blockers for hypertension).
C. This option is incorrect because it is a medication used for Parkinson's disease, not OAB.
D. This option is incorrect because it is a medication used for glaucoma, not OAB.

**Why the Correct Answer is Right:**
Option E (Oxybutynin) is a specific example of an antimuscarinic drug used to treat OAB. It acts as a competitive antagonist for acetylcholine at muscarinic receptors and has a high affinity for M3 receptors in the bladder wall.

**Clinical Pearl:**
In clinical practice, antimuscarinic drugs may be used in combination with other medications, such as beta-blockers or alpha-blockers, for comprehensive treatment of OAB symptoms. However, the choice of the specific antimuscarinic is crucial to ensure optimal efficacy and minimize side effects like dry mouth and constipation.