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Pharmacology > Antiparkinson Drugs > Flashcards

Antiparkinson Drugs Flashcards

1
Q

cardinal features of parkinsons

A

resting tremor, muscular rigidity, bradykinesia, gait impairment

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2
Q

principal metabolite of dopamine

A

HVA - homovanillic acid

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3
Q

what do the D1 and D2 receptors do

A
  • D1: activated adenylyl cyclase

- D2: inhibits adenylyl cyclase, opens K+ channels, suppresses Ca2+ currents

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4
Q

classification of drugs used to treat parkinsons

A

AAIDD

Amantadine
Antimuscarinics
Inhibitors of Dopamine Metabolism: COMT and MAO
Dopamine Precursors
Dopamine Receptor Agonists: Ergot and Non-ergot dopamine agonists

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5
Q

what is the dopamine precursor drug

A

Levodopa

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6
Q

mechanism of levodopa

A

transported into the brain by facilitative L transport system –> converted to dopamine in the brain using DOPA decarboxylase

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7
Q

what drug is given with levodopa and why

A

Carbidopa - Dopa decarboxylase inhibitor

  • it does not cross into the brain but works in the periphery by preventing conversion to dopamine in the periphery so that most of the L-DOPA can cause into the brain
  • also conversion to dopamine in periphery –> nausea, vomiting, cardiac arrhythmias, hypotension
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8
Q

what is Sinemet

A

preparation containing carbidopa and L-DOPA in fixed preparation

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9
Q

what is levodopa’s metabolite

A 
homovanillic acid (HVA)
dihydroxyphenylacetic acid (DOPAC)
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10
Q

what happens with long term use of levodopa

A

it is only effective for 3-5 years then responsiveness becomes lost completely

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11
Q

AE of levodopa

A 
GI effects (dopamine agonists cause nausea and vomiting)
CNS effects (Visual and auditory hallucinations and dyskinesia)
CVS effects (dopamine stimulates heart -- tachycardia)
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12
Q

what is the on-off phenomenon seen with levodopa

A

-off periods of marked akinesia alternate over on periods of improved mobility but often marked dyskinesia

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13
Q

contraindications of levodopa

A

HAV PAMP

  • Hypertensive crisis with Phenelzine or Tranylcypromine (MAOI)
  • Angle closure glaucoma
  • Vitamin B6 (co factor for L-dopa decarboxylase)
  • Psychotic patients esp if on Antipsychotics
  • Arrhythmias in cardiac patients
  • Melanoma
  • Peptic ulcers
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14
Q

what are the dopamine receptor agonists

A

Ergot derivatives: Bromocriptine

Non ergot derivatives: PARR
Pramipexole
Apomorphine
Ropinirole
Rotigotine
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15
Q

mechanism of bromocriptine and what is it used to treat

A

D2 agonist

Parkinsons
Hyperprolactinemia

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16
Q

mechanisms of the non ergot derivatives dopamine agonist

A

Pramipexole: preferential affinity for D3 receptors
Apomorphine: dopamine agonist
Ropinorole: purely D2 receptor agonist
Rotigotine: transdermal formulation that is dopamine agonist

17
Q

AE of the nonergot dopamine agonists (minus apomorphine)

A 
GI effects (nausea and vomiting)
CVS effects
Dyskinesia
Mental disturbances: hallucination etc
Somnolence

harder ones to reason out:
Pulmonary Infiltrates
Pleural and Retroperitoneal Fibrosis
Erythromelalgia

18
Q

long term complication of ergot derivatives dopamine agonist

A

painless digital vasospasm

19
Q

when is apomorphine usually used

A

in off periods of akinesia in patients on dopaminergic therapy

20
Q

since apomorphine is highly emetogenic, what pre treatment is usually used

A

Trimethobenzamide

Domperidone

21
Q

contraindication of apomorphine

A

5-HT3 antagonist -> profound hypotension and loss of consciousness

22
Q

AE of apomorphine

A

QT prolongation

23
Q

what are the inhibitors of dopamine metabolism

A

MAO inhibitors: Selegiline and Rasagiline

COMT inhibitors: Tolcapone and Entacapone

24
Q

what are the MAOIs used for in treatment of parkinson

A
  • Selegeline: selectively inhibits MAO-B so prevents breakdown of dopamine and enhances effect of levodopa (little chance for hypertensive crisis)
  • Rasagiline: prolongs effects of levodopa-carbidopa in parkinson patients
25
Q

what is Selegiline metabolized to and its importance

A

Methamphetamine and Amphetamine –> insomnia if taken after midafternoon

26
Q

what occurs when carbidopa is used together with levodopa (name the COMT inhibitors)

A

Tolcapone and Entacapone

-firstly inhibition of dopa decarboxylase by carbidopa –> increased in COMT in order to metabolized levodopa –> increases plasma 3-O-methyldopa (3-OMD) –> competes with levodopa for a carrier hence the levodopa that aren’t bound are not useful since they don’t get into the brain

27
Q

what is mechanism of COMT inhibitors

A

Tolcapone and Entacapone

decrease metabolism of levodopa
decreased 3-O-methyldopa (3-OMD)
increased uptake of levodopa
higher concentration of dopamine in the brain

28
Q

where do the COMT inhibitors exert their effect

A

Tolcapone in the central and periphery

Entacapone only periphery

29
Q

why is Entacapone preferred over Tolcapone

A
  • not associated with hepatotoxicity (TOLCAPONE LEADS TO HEPATIC NECROSIS)
  • available as fixed dose with levodopa/carbidopa
30
Q

AE of COMT inhibitors

A

Entacapone and Tolcapone

  • increased levodopa: dyskinesias, nausea, vomiting
  • fulminating hepatic necrosis with Tolcapone (every 2 week monitoring of liver function)
  • Orange discoloration of urine
31
Q

mechanism of amantadine in parkinsons

A

increase synthesis, release, or re-uptake of dopamine from surviving neurons

32
Q

AE of amantadine

A

Livedo Reticularis (lace like purplish discoloration of skin)

33
Q

contraindications/caution that should be taken in patient taken amantadine

A

caution in patients with history of seizures and heart failure

34
Q

antimuscarinics used in treatment of parkinsons

A

Benztropine

Trihexyphenidyl

35
Q

AE of the antimuscarinics

A

benztropine and trihexyphenidyl

xerostomia, pupillary dilation, dry mouth, other effects associated with anticholinergics

36
Q

contraindication of antimuscarinics

A

benztropine and trihexyphenidyl

Glaucoma
Prostatic Hypertrophy
Pyloric Stenosis

37
Q

most effective symptomatic treatment of Parkinsons

A

Levodopa with Carbidopa

38
Q

reduce motor fluctuations in patients with advanced disease

A

MAOI and COMT-I

39
Q

used for control of tremor and drooling

A

antimuscarinics

Pharmacology (79 decks)

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