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Anti-Parkinsonian Therapy & Drug Options

Apr 14, 2023

Anti-Parkinsonian Therapy Drug Options

As the name suggests, anti-Parkinson’s drugs are used to treat Parkinson’s disease. Anti-Parkinson’s drugs are an important part of Pharmacology. Read this entire blog post to know everything about these drugs and elevate your NEET PG preparation

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Parkinson’s Disease

  • Seen in the elderly population.
  • Symptoms:
    • Bradykinesia (slowing of movements)
    • Rigidity
    • Tremors
  • The Dopamine decreases, and the activity of Acetylcholine increases in the Substantia Nigra.

Aim of Anti-Parkinsonian Therapy

  1. ↑ Dopamine level
  2. ↓ Acetylcholine level
  3. MAO-B Inhibitor
  4. COMT Inhibitors
  5. D2 Agonist

Increase the level of Dopamine.

  • Dopamine acts on the D2 receptor.
  • Dopamine can not be given orally due to Dopamine can not cross BBB (Blood-brain barrier). Due to that, Dopamine is given with levodopa (Pro-drug). Inhibit Enzyme COMT and MOA-B to increase the level of Dopamine. Giving a D2 agonist drug increases the Dopamine level.


Levodopa (Pro-drug)

  • It has a very short half-life (t ½ = 1-2 hr). Levodopa ⇒ crosses BBB ⇒ Dopamine. In central levodopa is metabolized to dopamine with the help of Central decarboxylase enzyme. Levodopa metabolized in the periphery ⇒ Dopamine with the help of peripheral decarboxylase enzyme.

Drug Interaction L-Dopa

  • Levodopa should not combine with D2 blockers. 

Ex. Typical Anti-psychotic, Metoclopramide

  • Levodopa + Vitamin B6 ⇒ ↓ Levodopa efficacy
Vitamin B 6 is the stimulator of peripheral decarboxylase.Levodopa-induced Nausea, vomiting ⇒ Rx. Domperidone

Contraindication of L-Dopa

  • L-dopa is not used in a patient with acute psychosis.
  • Not used in a patient with gastric ulcer.
  • Not used in a patient with Angle-closure glaucoma.

 Why is carbidopa combined given with L-dopa? 

  • Diminished peripheral metabolism of L-dopa in GIT and other tissues (thus increasing t₁/2). Increase availability of levodopa to CNS. Reduce the dose of levodopa and its side effects.
  • Important ⇒ Levodopa: carbidopa: 4:1

Advantages of The Combination of Carbidopa With L-Dopa

  • Levodopa becomes long acting in brain. Peripheral adverse effects not seen. Decreases the episode of Parkinson.

Disadvantages of the Combination of Carbidopa With L-Dopa 

  • No ↓ psychosis. No ↓ dyskinesis. No ↓ Postural hypotension

MAO-B Inhibitor (Monoamine Oxidase)

Drugs Acting On MAO

Selegiline (Doprenyl)

  • Pk ⇒ Metabolized ⇒ Amphetamine ⇒ Seizures. It increases Dopamine activity ⇒ develops psychosis symptoms. Advantage is neuroprotective effect.


  • It has 5 times more potent. It is not metabolized to amphetamine.


  • New MAO Inhibitor approved for Parkinson’s disease.

COMT Inhibitors (Catechol Ortho Methyltransferase)

  • Levodopa can be metabolized by COMT into 3-O -methyldopa. Entacapon Does not cross BBB. Tolcapone ⇒ BBB (Inhibit in periphery and central COMT). Tolcapone shows Hepatotoxicity.

D2 Agonist

Ergot Derived 

  • Drugs: Bromocriptine, Cabergoline, Pergolide
  • Adverse Effects
  • Vasoconstriction ⇒ Gangrene
  • Fibrosis

Non- Ergot derived. 

  • Drugs: Ropinorole, Pramipexole, Rotigotine [Available as transdermal patch]
  • Uses
  • Parkinson’s disease
  • Restless Lung syndrome 
  • Adverse Effect
  • Increase Compulsive behaviour like Hypersexuality, Gambling, Kleptomania


  • It is a non-ergot derived drug. Given as S.C. Injection
  • Rx: Acute off Episodes
  • Adverse Effects
    • Nausea 
    • Vomiting

Important Information DOC for restless leg syndrome is Gabapentin.

Decreased ACH Level

Drugs ↓ Ach level is called Central anticholinergics.

Drugs Lowering Ach Level

Central anticholinergicsBenzhexol (Trihexyphenidyl)BenztropineBiperidenAntihistamines with anticholinergic propertiesPromethazine. DiphenhydramineDimenhydrinate


  • Amantadine produces Anti-dyskinetic properties. It Produces NMDA Antagonism. It has Anti-cholinergic properties.
  • Adverse effects
  • Livedo reticularis
  • Ankle oedema

Newer Drugs For Parkinson Disease

  • Opicapone COMT Inhibitor: To decrease off episodes of Parkinson disease.
  • Istradephylline Adenosine antagonist: To decrease episodes Off Parkinson Disease.

And that is everything you need to know about anti-Parkinson’s drugs for your Pharmacology paper. For more informative and interesting blog posts like this, download the PrepLadder App and keep following our blog!

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