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Pharmacology > Anti-Parkinson Drugs > Flashcards

Anti-Parkinson Drugs Flashcards

(50 cards)

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1
Q

Cardinal features of Parkinson

A
  • Resting tremor
  • Muscle rigidity (Cogwheel rigidity)
  • Bradykinesia
  • Gait impairment
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2
Q

Etiology of Parkinson

A

Loss of neurons in the Dopaminergic Nigrostriatal pathway

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3
Q

Dopamine Synthesis

A
  • Tyrosine (transported across BBB by System-L in a Na-independent manner)
  • Tyrosine (Tyrosine hydroxylase - RLS) –> DOPA (DOPA Carboxylase) –> Dopamine

Inc Dopamine formation by Inc substrates

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4
Q

Dopamine receptors related to Parkinson

A
  1. D1 Receptors
    - Inc adenylyl cyclase
  2. D2 Receptors
    - Dec adenylyl cyclase
    - Inc K conductance
    - Dec Ca conductance

Treatment of Parkinson is mostly focused on D2 but needs D1 for maximal effect

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5
Q

Dopamine pathways in Brain

A
  1. Nigrostriatal
    - Make focus for PD - Destruction of neurons
  2. Mesolimbic
  3. Mesocortical
  4. Tuberoinfundibular
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6
Q

Pathophysiology of Parkinson Disease

A

NORMAL
GABAergic output from Striatum
- Inhibited by Dopaminergic neuron in Substantia nigra
- Stimulated by Cholinergic neurons

PARKINSON

  • Destruction of Dopaminergic neurons in Nigrostriatal pathway –> Loss of muscle control/ movement
  • 70% neuron loss for symptoms to appears
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7
Q

Aim of Anti-Parkinson Drugs

A
  1. Restoring dopamine in basal ganglia

2. Antagonizing the excitatory effect of cholinergic neurons

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8
Q

Classes of Drugs used to treat Parkinson

A

1 Drugs that restore Dopamine actions

  • Dopamine precursors
  • Dopamine receptor agonists
  • Inhibitors of Dopamine metabolism
  • Amantadine
  1. Acetylcholine Antagonists
    - Antimuscarinics
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9
Q

Dopamine Precursors (Names)

A

Levodopa

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10
Q

Mechanism of Levodopa

A

Levodopa is a precursor for Dopamine

Levodopa is transported into CNS and converted to Dopamine by Dopa-carboxylase (mostly in the periphery)
- Restores dopamine in the Extrapyramidal centers

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11
Q

Why does the effects of Levodopa decrease as the disease progress.

A

As the disease progresses there are less neurons so less Levodopa can be taken up and converted to Dopamine.

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12
Q

Function of Carbidopa

A

Dec the metabolism of Levodopa in the GI tract & periphery tissues –> Inc Levodopa availability to CNS

Levodopa–> GI= 70%, Periphery = 28% & Brain - 2%
Sinemet –> GI = 40%, Periphery = 50% & Brain = 10%

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13
Q

Sinemet

A

Dopa preparation of both Carbidopa & Levodopa in fixed proportions
- 1:10 OR 1:4

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14
Q

Pharmacokinetics of Levodopa

A
  • Rapid absorption in SI
  • Food delays appearance in plasma
  • Some A.a compete w/ drug for absorption from gut
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15
Q

Clinical uses & Response to Levodopa

A

Levodopa/Carbidopa –> DOC for PD treatment

  • Response decrease w/ 3-5 years of therapy
  • Response completely lost overtime due to lost of neurons
  • Does NOT stop PD progression; just helps with symptom management
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16
Q

Adverse effects of Levodopa

A

GI
- Anorexia, Nausea & vomiting

CVS
- Tachycardia, Ventricular extrasystoles & Hypotension

CNS
- Hallucinations (visual & auditory), Dyskinesias, Mood changes, Depression, Anxiety, Agitation & Insomnia

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17
Q

Fluctuations in Response to Levodopa

A
  1. Wearing-Off Reactions
  2. On-Off Phenomenon
    - switch between mobility and immobility in levodopa-treated patients, which occurs as an end-of-dose
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18
Q

Interactions & Contraindications of Levodopa

A

Do NOT give:

  • Psychotic pts/ Concomitant antipsychotic use - worsen symptoms
  • Angle-closure glaucoma - activate D1 receptors in eyes which Inc aqueous humour production & ICP
  • Nonspecific MAOI concomitant use - Hypertensive crisis

MONITOR/

  • Cardiac pts- Arrhythmias
  • Anti-HTN drug use - Orthostatic Hypotension
  • Active peptic ulcer - GI bleeding
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19
Q

Dopamine Receptor Agonist (class & names)

A
  1. Ergot Dopamine Agonists
    - Bromocriptine
  2. Non-ergot Dopamine Agonists
    - Pramipexole
    - Ropinirole
    - Rotigotine

Does NOT require enzymatic conversion - Do NOT depend on the functional capabilities of Nigrostriatal neurons

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20
Q

Bromocriptine

A
  • D2 agonist

- Rarely used now

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21
Q

Pramipexole & Ropinirole

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A
  • Initial treatment of PD for younger pts.
  • Well tolerated
  • Less effective than Levodopa in treating motor symptoms; but less likely to cause motor fluctuation & dyskinesia
  • Older pts. are more vulnerable to cognitive AE
22
Q

Rotigotine

Study These Flashcards
A
  • Transdermal formulation - Once-daily use
23
Q

GI Adverse effects of Dopamine Agonists

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A
  • Anorexia
  • Nausea & vomiting
  • Constipation
  • Peptic ulcer bleeds
24
Q

CVS Adverse effects of Dopamine Agonists

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A
  • Postural hypotension
  • Cardiac arrhythmias
  • Peripheral edema
  • Painless digital vasospasm (Ergot agonists)
25
Motor & Mental Adverse effects of Dopamine Agonists
- Abnormal movements - Confusion - Hallucinations & Delusions - Compulsive behaviors
26
Other Adverse effects of Ergot Dopamine Agonists
- Headache - Nasal congestion - Inc arousal - Pulmonary infiltrates - Pleural & retroperitoneal fibrosis - Erythromelalgia
27
Other Adverse effects of Non-ergot Dopamine Agonists
Uncontrollable Somnolence | - Discontinue use
28
Drug Interactions of Dopamine Agonists
- Antipsychotic drugs antagonize Dopamine - Dec efficacy | - CNS depressants -Inc somnolence & confusion
29
Contraindication of Dopamine agonists
- Hx of psychotic illness - Recent MI - Active Pectic Ulcer
30
Rescue therapy
APOMORPHINE (Non-ergot agonists) - Treatment of "off episodes" of akinesis in pts on dopaminergic therapy - Pretreatment w/ antiemetic agent TRIMETHOBENZAMIDE
31
Why is Trimethobenzamide used before Apomorphine
Apomorphine is an Emetogenic agent so pretreatment with an antiemetic agent is recommended
32
Adverse effects of Apomorphine
- QT prolongation - Dyskinesia - Drowsiness - Sweating - Hypotension
33
Inhibitors of Dopamine Metabolism (class & name)
1. MAO Inhibitors - Selegiline - Rasagiline 2. COMT Inhibitors - Tolcapone - Entacapone
34
Selegiline MOA
Inhibits MAO-B --> Stops Dopamine breakdown in brain - Selective to MAO-B - Irreversible
35
Clinical uses of Selegiline
Adjunct to Levodopa | - Allows Levodopa dose to be reduced & therefore enhances its effects
36
Metabolism of Selegiline
Metabolized to - Methamphetamine - Amphetamine
37
Adverse effects of Selegiline
Insomnia (due to presence of metabolites) Should NOT be used late evenings
38
Rasagiline
MAO-B Inhibitor | - Irreversible
39
MAO-I Drug Interactions
1. MAOI + Serotonergics --> Hypertensive crisis & Serotonin syndrome 2. MAOI + Sympathomimetic amines --> Severe HTN
40
MOA of COMT Inhibitors
NORMAL - COMT breaks down Levodopa to 3-o-methyl dopa which competes with Levodopa for transport across the intestinal mucosa & BBB COMT-I prevent the formation of 3-0 methyl dopa
41
Amantadine
42
Antimuscarinics (names)
- Benztropine | - Trihexyphenidyl
43
Contraindications of Amantadine
CAUTION w/: - Hx of seizures - Hx of Heart failure
44
Adverse effects of Amantadine
- Restlessness, agitation, confusion & hallucinations - Acute toxic psychosis (High- dose) - Headache, Heart failure, Orthostatic hypotension, Dry mouth, Urinary retention & GI disturbances - Peripheral edema - Livedo reticularis - rash that usually clears within a month of drug discontinuation
45
Adverse effects of COMT Inhibitors
- Fulminating Hepatic Necrosis (Tolcapone)
46
Clinical uses of Antimuscarinics
ADJUVANT therapy - may improve tremor & rigidity - little effect on bradykinesia
47
Adverse effects of Antimuscarinics
- Mood changes - Xerostomia - Pupillary dilation - Confusion - Hallucinations - Urinary retention
48
Contraindications of Antimuscarinics
- Glaucoma - Prostatic hypertrophy - Pyloric stenosis
49
How to control the Peripheral edema caused by Amantadine?
Diuretics
50
Carbidopa
Dopa Decarboxylase Inhibitor - Does NOT cross the BBB - Given in combination w/ Levodopa

Pharmacology (16 decks)

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