**Core Concept**
Pirenzepine is a selective M1 muscarinic receptor antagonist, which is used to treat peptic ulcer disease by reducing gastric acid secretion. This is in contrast to non-selective anticholinergics that can cause unwanted side effects by blocking M2 receptors in the heart.

**Why the Correct Answer is Right**
Pirenzepine works by selectively inhibiting the M1 muscarinic receptors in the stomach, leading to a reduction in gastric acid secretion. This results in a decrease in the formation of gastric ulcers and an improvement in symptoms. In contrast, non-selective anticholinergics like atropine can cause unwanted side effects such as tachycardia and dry mouth due to their blockade of M2 receptors in the heart and other muscarinic receptors.

**Why Each Wrong Option is Incorrect**
**Option A:** Dicyclomine is a non-selective anticholinergic that is used to treat irritable bowel syndrome and other gastrointestinal disorders. It does not have a role in the treatment of peptic ulcer disease.
**Option B:** Methacoline is actually a cholinergic agonist, not an anticholinergic. It is used to treat bronchial asthma and other respiratory conditions.
**Option D:** Aclidinium is a long-acting muscarinic antagonist that is used to treat chronic obstructive pulmonary disease (COPD). While it is an anticholinergic, it is not used for the treatment of peptic ulcer disease.

**Clinical Pearl / High-Yield Fact**
When treating peptic ulcer disease, it is essential to choose an anticholinergic that is selective for the M1 muscarinic receptors to avoid unwanted side effects. Pirenzepine is a good example of such a medication.

**✓ Correct Answer: C. Pirenzepine**