**Core Concept**
Domperidone is a peripherally selective dopamine D2 receptor antagonist used primarily for its antiemetic and prokinetic effects. It works by blocking dopamine receptors in the gastrointestinal tract, thereby increasing gastrointestinal motility and reducing nausea.

**Why the Correct Answer is Right**
Domperidone's peripheral selectivity is due to its inability to cross the blood-brain barrier, allowing it to exert its effects on the gastrointestinal tract without affecting the central nervous system. This is in contrast to other dopamine antagonists like metoclopramide, which can cross the blood-brain barrier and cause central side effects. Domperidone's mechanism of action involves blocking dopamine receptors in the gastrointestinal tract, which leads to increased acetylcholine release and subsequent increased gastrointestinal motility.

**Why Each Wrong Option is Incorrect**
**Option A:** This option may be incorrect, but without the full text, it's difficult to evaluate. If it's a true statement, it would be an accurate description of domperidone's effects.
**Option B:** This option may be incorrect, but without the full text, it's difficult to evaluate. If it's a false statement, it would be due to a misunderstanding of domperidone's pharmacokinetics or pharmacodynamics.
**Option C:** This option may be incorrect, but without the full text, it's difficult to evaluate. If it's a false statement, it would be due to a lack of understanding of domperidone's mechanism of action.
**Option D:** This option is incorrect because domperidone is a dopamine D2 receptor antagonist, not an agonist. This is a fundamental difference in its mechanism of action.

**Clinical Pearl / High-Yield Fact**
Domperidone is often used in patients with Parkinson's disease, as it can help manage nausea and vomiting without exacerbating the disease. However, it's essential to be aware of its potential interactions with other medications and its effects on the gastrointestinal tract.

**Correct Answer: D. Domperidone is a dopamine D2 receptor antagonist, not an agonist.**