**Core Concept**
Salivary gland hypofunction is a common side effect of cancer chemotherapy, leading to dry mouth (xerostomia). The treatment of xerostomia involves stimulating salivary gland function or replacing missing saliva. Medications play a crucial role in managing this condition.

**Why the Correct Answer is Right**
Pilocarpine is a muscarinic receptor agonist that stimulates the parasympathetic nervous system, leading to increased salivary gland secretion. It works by binding to muscarinic receptors in the salivary glands, promoting the release of acetylcholine and subsequent saliva production. This medication is specifically indicated for the treatment of xerostomia in patients undergoing radiation therapy for head and neck cancer or those experiencing xerostomia as a result of Sjögren's syndrome.

**Why Each Wrong Option is Incorrect**
**Option A:** Amifostine is a cytoprotective agent used to reduce the risk of nephrotoxicity and ototoxicity in patients receiving cisplatin-based chemotherapy. It does not have any significant effect on salivary gland function.
**Option B:** Olanzapine is an atypical antipsychotic medication that can cause xerostomia as a side effect, rather than treating it.
**Option C:** Metoclopramide is a dopamine antagonist with antiemetic properties, which can also cause xerostomia as a side effect.

**Clinical Pearl / High-Yield Fact**
When managing xerostomia in cancer chemotherapy patients, consider the use of pilocarpine or other salivary stimulants to improve oral health and quality of life.

**Correct Answer:** C. Pilocarpine is a muscarinic receptor agonist that stimulates salivary gland secretion, making it an effective treatment for dry mouth in cancer chemotherapy patients.