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Pharm > Parkinsonism > Flashcards

Parkinsonism Flashcards

1
Q

The MPTP Story

A
  • (1-methyl-4-phenyl-1,2,3,6-tetrahydorpyridine)
  • neurotoxin that can cause Parkinson disease
  • metabolized to MPP radical
  • symptoms reversed by antiparkinson drugs
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2
Q

2 pathways that involve dopamine

A
  • two pathways that involve dopamine
  • at the D1 receptor is stimulation of the direct pathway
  • at the D2 receptor is inhibition of the indirect pathway
  • net result of dopamine acting at D1 or D2 is an enhancement of excitatory input to the cerebral cortex
  • loss of nigrostriatal dopamine neurons no stimulation to D1 or D2 receptors
  • increase of GABA (inhibitory) inputs to the cerebral cortex
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3
Q

Ach

A
  • acetylcholine-not exactly in the wiring of this circuit, but dopamine inhibits acetylcholine release in the striatum, so when the dopamine is lost an increase of acetylcholine prevails
  • enhanced GABA transmission due to acetylcholine
  • therefore the balance between excitatory and inhibitory inputs is greatly out of balance
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4
Q

THERAPY OF PARKINSON DISEASE

A

1) increase dopamine
(2) direct acting dopamine receptor agonists
(3) dopamine storage uptake/release
(4) inhibit MOA-B
(5) anticholinergics
(6) inhibit COMT

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5
Q

LEVODOPA

A
  • metabolic precursor of dopamine
  • it is the single most effective agent in the treatment of PD
  • inert- therapeutic and adverse effects result from the decarboxylation of levodopa to dopamine in dopaminergic neurons in the striatum
  • crosses the blood-barrier by an active process by a carrier of aromatic amino acids
  • in real life levodopa in formulated together with a peripheral L-aromatic amino acid decarboxylase inhibitor (carbidopa) levodopa/carbidopa(SINEMET)
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6
Q

L-DOPA cont.

A
  • without the inhibitor, very little levodopa reaches the brain (1%) it is metabolized in the liver, kidney and G.I. tract.
  • levodopa causes a lot of G.I. problems (N/V), the combo decreases this effect
  • can be used in all types of Parkinson disease except if caused by antipsychotic therapy
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7
Q

L-DOPA CONT.

SIDE EFFECTS

A

-TWO CLASSES
(1) early in treatment-nausea, vomiting, orthostatic hypotension tachycardia, arrhythmias (dopaminergic action on the heart) usually become tolerant to these effects.——-saliva and urine is brown color
(2) increasing duration of therapy——result from the central stimulation of dopamine receptors—dyskinesias-abnormal choreiform movements of the limbs, hands, trunk, and tongue,—–occurs in 45 to 90% of patients—mechanism???—hypersensitive receptors-decrease dose but Parkinson symptoms come back
mental disturbances—hallucinations, wild dreams, delusions

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8
Q

L-DOPA CONT.

phenomenon

A

On-Off phenomenon-when blood levels of levodopa drop, immediate reversal of symptoms—develops after 2 years of therapy—-use sustained release formulation
—don’t take pyridoxine (B6) –increases peripheral breakdown of levodopa

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9
Q

BROMOCRIPTINE

A

agonist at D2 receptors partial antagonist at D1 receptors

(2) can cause dyskinesias
(3) can cause orthostatic hypotension
(4) can cause serious cardiac problems, patients with history of MI
(5) can cause mental disturbances as levodopa
(6) can cause used as an adjunct with levodopa to lessen the on/off phenomenon in advance cases
(7) may save other dopaminergic neurons from oxidative stress
(8) ergot like-cause pleuropulmonary and retroperitoneal fibrosis

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10
Q

PERGOLIDE

A

no longer on the market- heart valve fibrosios due to activation of 5HT 2B receptors!!!!!!!!!!!!!!

(1) agonist at both D1 and D2 receptors, more potent than bromocriptine
(2) ergot like-cause pleuropulmonary and retroperitoneal fibrosis

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11
Q

(C) PRAMIPEXOLE (MIRAPEX)

D) ROPINIROLE (REQUIP

A

(1) both are non-ergot dopamine agonists at D2 and D3 receptors
(2) both are used as first-line and also adjunctive
(3) both are used best in patients that have not had levodopa therapy
(4) both may delay the need for levodopa
(5) both have less hallucinations and orthostatic hypotension like the ergot agonists
(6) Both may cause daytime sedation during normal activities
(7) pramipexole-renal elimination—cimetidine inhibits renal tubular secretion of organic bases—increases pramipexole half-live by 40%
(8) Ropinirole & Pramipexole is also used to treat restless leg syndrome & fibromyalgia. Also may cause reward seeking compulsive behavior- binge drinking, shopping, and gambling

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12
Q

AMANTADINE

A
  • antiviral drug used in the treatment of influenza
  • MOA-alters dopamine release (if at max no effect)or uptake also has anticholinergic effects
  • orthostatic hypotension, dry mouth, hallucinations
  • little effect on tremor, but is more effective than anticholinergics against rigidity and bradykinesia
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13
Q

SELEGILINE

A

MONOAMINE OXIDASE B INHIBITOR
-both MAO-A and MAO-B are present in the periphery, MAO-B is the predominate form in the Striatum—–responsible for the majority of oxidative metabolism of dopamine in the brain
low doses does not MAO-A, but in high doses will get peripheral effects(severe hypertension)
-enhances the levodopa

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14
Q

ANTIMUSCARINIC AGENTS

A

TRIHEXYLPHENIDYL (ARTANE)

BENZTROPINE (COGENTIN)

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15
Q

TRIHEXYLPHENIDYL (ARTANE)

BENZTROPINE (COGENTIN)

A
  • blockage of cholinergic transmission to augment dopamine
  • have modest antiparkinsonian action
  • used as adjunct with levodopa
  • same side effects as high dose atropine
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16
Q

TOLCAPONE

A

COMT INHIBITORS

(1) selectively inhibits catechol-o-methyl transferase (COMT)-normally a minor pathway of levodopa metabolism, but with carbidopa blocking peripheral decarboxylase a significant amount of 3-O-methyldopa is formed that competes with levodopa for active transport into the CNS
(2) inhibition of COMT –deceased 3-O-methydopa results in an increase central uptake of levodopa
(3) useful in the On-Off phenomenon
(4) can be hepatotoxic, —-measure hepatic enzymes
(5) can cause blood dyscrasias
(6) long acting

17
Q

ENTACAPONE

A

(1) same MOA as tolcapone
(2) not hepatotoxic
(3) does not cause blood dyscrasias
(4) short acting, usually administered with each dose of levodopa/carbidopa

18
Q

Alzheimers

A

acetylcholinesterase inhibitors

N-methyl-D-aspartate receptor antagonist

19
Q

acetylcholinesterase inhibitors

A

(1) TACRIN (COGNEX)
- hepatotoxic
(2) DONEPEZIL(ARICEPT)
(3) RIVASTIGMINE (EXELON)

20
Q

N-methyl-D-aspartate receptor antagonist

A

(1) MEMANTINE (EBIXA)
Over stimulation of NMDA receptors by glutamate, permits calcium to flow freely into the cell, sustained overexposure of the cell, leads to cellular degeneration

21
Q

SYMPTOMATIC TREATMENT OF AD

A

DEPRESSION-SSRI’s

CITALOPRAM (CELEXA), ESCITALOPRAM (LEXAPRO)-S,ent
PAROXETINE (PAXIL)
SERTALINE (ZOLOFT)
FLUOXETINE (PROZAC)

PSYCHOSIS and AGITATION

Atypical Antipsychotic’s

(1) RISPERIDONE (RISPERIDONE)
(2) OLANZAPINE (ZYPREXA)
(3) QUETIAPINE (SEROQUEL

Pharm (21 decks)

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