A 60-year-old man with Parkinson's disease is started on a drug that selectively blocks muscarinic M1 receptors in the striatum with minimal peripheral effects. Which drug best fits this profile?
- A Atropine
- B Trihexyphenidyl ✓
- C Pirenzepine
- D Ipratropium
Correct answer: B. Trihexyphenidyl
Explanation
Trihexyphenidyl (Benzhexol) is a centrally acting antimuscarinic used in Parkinson's disease to reduce tremor and rigidity by blocking M1 receptors in the corpus striatum. Pirenzepine selectively blocks M1 receptors in gastric parietal cells peripherally. Atropine is non-selective, and ipratropium is a quaternary ammonium compound that does not cross the blood-brain barrier.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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