📌 Introduction
Parkinson’s disease is a chronic neurodegenerative disorder that mainly affects movement. It is characterized by tremors, rigidity, and slow movements (bradykinesia). The disease occurs due to a deficiency of dopamine in the brain, especially in the substantia nigra region.
This topic is highly important for GPAT, DSSSB, and other pharmacy competitive exams.
📍 Pathophysiology of Parkinson’s Disease
Parkinson’s disease results from degeneration of dopaminergic neurons in the substantia nigra. This leads to decreased dopamine levels and an imbalance between dopamine and acetylcholine in the basal ganglia.
👉 Key concept:
Low dopamine + high acetylcholine = motor symptoms
✒️ Symptoms of Parkinson’s Disease
• Resting tremor
• Muscle rigidity
• Bradykinesia (slowness of movement)
• Postural instability
• Mask-like face
• Shuffling gait
📝 Classification of Drugs Used in Parkinson’s Disease
1. Dopamine Precursors
• Levodopa (converted into dopamine in brain)
2. Peripheral DOPA Decarboxylase Inhibitors
• Carbidopa (given with levodopa to increase its effectiveness)
3. Dopamine Agonists
• Bromocriptine
• Pramipexole
4. MAO-B Inhibitors
• Selegiline
• Rasagiline
5. COMT Inhibitors
• Entacapone
6. Anticholinergic Drugs
• Trihexyphenidyl
• Benztropine
🧬 Mechanism of Action
• Levodopa → converted to dopamine in CNS
• Carbidopa → prevents peripheral breakdown of levodopa
• Dopamine agonists → directly stimulate dopamine receptors
• MAO-B inhibitors → prevent dopamine breakdown
• COMT inhibitors → prolong levodopa action
• Anticholinergics → reduce acetylcholine activity
👉 Overall effect: Restore dopamine-acetylcholine balance
🩺 Pharmacological Effects
• Improves motor control
• Reduces tremors and rigidity
• Enhances voluntary movement
• Improves quality of life
💊 Therapeutic Uses
• Parkinson’s disease
• Drug-induced parkinsonism (antipsychotic-induced)
🚨 Side Effects
• Nausea and vomiting
• Orthostatic hypotension
• Dyskinesia (involuntary movements)
• Hallucinations
• Confusion
🪫Drug Interactions
• Levodopa + Vitamin B6 → reduces effect
• Avoid with non-selective MAO inhibitors
• Antipsychotics may reduce effectiveness
🟢 Contraindications
• Psychotic disorders
• Narrow-angle glaucoma
• Severe cardiac disease
• Caution in elderly patients
📑 Important Exam Points
• Levodopa + Carbidopa → gold standard therapy
• Long-term use → dyskinesia
• Selegiline → MAO-B inhibitor
• Anticholinergics → useful in tremor
🎯 Conclusion
Parkinson’s disease drugs work by increasing dopamine levels or reducing its breakdown. Understanding classification, mechanism, and side effects is essential for pharmacology exams and clinical knowledge.
👉 Practice MCQs in evening post
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