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.
Seen in the elderly population.
Bradykinesia (slowing of movements)
TheDopamine decreases, and the activity of Acetylcholine increasesin the Substantia Nigra.
Aim of Anti-Parkinsonian Therapy
↑ Dopamine level
↓ Acetylcholine level
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 increasesthe Dopamine level.
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
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.
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.
Drugs: Bromocriptine, Cabergoline, Pergolide
Vasoconstriction ⇒ Gangrene
Non- Ergot derived.
Drugs: Ropinorole, Pramipexole, Rotigotine [Available as transdermal patch]
Restless Lung syndrome
Increase Compulsive behaviour like Hypersexuality, Gambling, Kleptomania
It is a non-ergot derived drug. Given as S.C. Injection
Rx: Acute off Episodes
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)BenztropineBiperiden
Antihistamines with anticholinergic propertiesPromethazine. DiphenhydramineDimenhydrinate
Amantadine produces Anti-dyskinetic properties. It Produces NMDA Antagonism. It has Anti-cholinergic properties.
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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