## Mechanism of MAO-B Inhibition **Key Point:** Selegiline is a selective, irreversible inhibitor of monoamine oxidase type B (MAO-B), the enzyme responsible for the catabolism of dopamine in the brain. **High-Yield:** At therapeutic doses (≤10 mg/day), selegiline shows selectivity for MAO-B over MAO-A, avoiding the "cheese effect" (hypertensive crisis) seen with non-selective MAOI inhibitors. ## Clinical Role in Parkinsonism Selegiline is used as: - **Adjunctive therapy** with levodopa to reduce "off" periods - **Monotherapy** in early-stage PD to delay progression - Increases dopamine availability by preventing its breakdown ## Why Other Options Are Wrong | Drug | Class | Mechanism | |------|-------|----------| | Entacapone | COMT inhibitor | Blocks catechol-O-methyltransferase; prolongs levodopa action | | Amantadine | NMDA antagonist | Blocks glutamate; anti-parkinsonian via unknown mechanism | | Trihexyphenidyl | Anticholinergic | Blocks muscarinic receptors; treats tremor & rigidity | **Clinical Pearl:** Selegiline's neuroprotective effects (if any) remain debated, but it is the only MAO-B selective agent in the parkinsonian armamentarium [cite:KD Tripathi 8e Ch 12].
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.