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Pharmacology 1 > Antiparkinsonian Drugs > Flashcards

Antiparkinsonian Drugs Flashcards

1
Q

Name 2 classes of antiparkinsonian drugs

A

Drugs affecting brain dopaminergic system
Drugs affecting brain cholinergic system

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2
Q

Classy drugs affecting brain dopaminergic system

A

Dopamine agonist: Levodopa
Peripheral decarboxylase inhibitor: Carbidopa, Banserazide
COMT inhibitor: Entecapone, Tolcapone
MAO-B inhibitor: Selegiline, Rasagiline
Dopaminergic agonist: Bromocriptine
Glutamate (NMdA receptor) agonist: Amantadine

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3
Q

Classify drugs affecting brain cholinergic system

A

Central anticholinergics: Trihexyphenydyl, Procylidine, Biperiden
Antihistamines: promethazine, diphenhydramine

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4
Q

Actions of Levodopa in CNS

A
  1. symptomatic relief. Hypokinesia and rigidity resolve first followed by tremors. Secondary symptoms like gait, posture, handwriting, speech etc gradually normalized.
  2. General alerting response which can cause hyperexcitability and psychosis.
  3. Dementia if present changes to psychiatric symptoms
  4. Non specific awakening in hepatic coma
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5
Q

Extra CNS actions of levodopa

A
  1. Heart: peripherally formed DA can cause tachycardia by stimulating B adrenergic receptors. No rise in BP and causes postural hypotension due to central action, excess DA and Na in brain decrease sympathetic outflow
  2. CTZ: excitatory effect. Cause nausea and vomiting
    Endocrine: inhibit prolactin release and increase GH release
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6
Q

Bioavailability of levodopa affected by

A
  1. Slow gastric emptying
  2. Amino acids present in food compete for same carrier
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7
Q

ADR of Levodopa

A

At initiation of therapy
1. Nausea and vomiting
2. Postural hypotension
3. Cardiac arrhythmia
4. Exacerbation of angina
5. Alteration in taste sensation

Due to prolonged therapy
1. Abnormal movements(dyskinesia)
2. Behavioral effects
3. Fluctuation in motor performances

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8
Q

Contraindications of Levodopa

A

Ischemic heart disease
CV diseases
Hepatic and renal disease
Psychiatric
Malignant melanoma
Peptic ulcer

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9
Q

Interactions of levodopa

A

Pyridoxine: increases peripheral conversion
Phenothiazine, metoclopramide reverse the effect
Non selective MAO inhibitors: prevent degradation of NA and DA
Antihypertensives: postural hypotension
Atropine and central anticholinergics

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10
Q

Advantages of using carbidopa with levodopa

A
  1. Plasma T 1/2 of levodopa prolonged
  2. Systemic concentration reduced hence minimal nausea and vomiting
  3. Cardiac complications reduced
  4. Pyridoxine reversal doesn’t occur
  5. On- off effect minimized
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11
Q

What is Co-careldopa

A

Combination of levodopa and carbidopa

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12
Q

Why selective MAO B inhibitor

A

Both present in peripheral adrenergic structures but MAO B predominates in brain and blood platelets. No peripheral action hence no accumulator of CA and hypertensive reaction because of metabolism of NA

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13
Q

ADR of selegiline

A

Postural hypotension
Nausea
Vomiting
Confusion
Psychosis
Dyskinesia
Partially metabolized by liver to amphetamine which causes insomnia and agitation

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14
Q

How is Rasagiline different from Selegiline

A

Not metabolized by liver to amphetamine

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15
Q

Mechanism of action of COMT inhibitor

A
  1. When peripheral conversion od Levodopa is blocked by using carbidopa, it is mainly metabolized to 3-O-Methyl dopa by COMT, hence blocked prolongs T1/2 of levodopa
  2. COMT also plays a role in degradation of Levodopa in brain hence can block it as well. Only Tolcapone
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16
Q

Name some COMT inhibitor

A

Entecapone
Tolcapone

17
Q

ADR of COMT inhibitor

A

Nausea vomiting
Dyskinesia
Postural hypotension
Hallucination
Diarrhea
Yellowish discoloration of urine

18
Q

Action of amantadine

A

It promotes presynaptic synthesis and release of DA in brain and has an antagonistic action on NMDA type of glutamate receptors.

19
Q

Side effect of Amantadine

A

Livedo Reticularis
Insomnia
Restlessnes
Nightmares
Anticholinergics effects

20
Q

Why is central anticholinergics used in PD

A

To reduce the unbalance between dopaminergic (inhibitory) and adrenergic (excitatory) in the brain

21
Q

Examples of central anticholinergics

A

Trihexyphenidyl/ Benzhexol
Procyclidine

22
Q

Major use of central anticholinergics

A

Drug induced Parkinsonism

Pharmacology 1 (14 decks)

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