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25 Cards in this Set
- Front
- Back
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Phenothiazides and Haloperidol
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- Block dopamine receptors
- Can produce and exacerbate Parkinson symptoms |
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What is the mechanism of action of Levodopa?
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- Metabolic precursor of dopamine
- Can cross the BBB unlike dopamine itself - Readily transported into the CNS - Converted to Dopamine in the brain |
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What is a drawback to using Levodopa by itself?
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Much of the drug is decarboxylated to dopamine in the periphery and GI tract before making it to the CNS and brain
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What are the drawbacks to Levodopa's pharmacokinetics?
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- It has an extremely short half-life
- This causes fluctuations in plasma concentrations - This in turn, leads to the "on-off" phenomenon of Parkinson symptoms |
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- What class of drugs are counterindicated for use with Levodopa?
- What is the main result of this drug interaction? |
- Non-specific MAO Inhibitors (e.g. Phenelzine)
- They can lead to a hypertensive crisis |
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Carbidopa mechanism of action?
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It is a Dopamine decarboxylase inhibitor
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What are the advantages of using Carbidopa?
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- It diminishes the metabolism of Levodopa in the GI tract and peripheral tissues
- It increases the availability of Levodopa to the CNS - It helps to lower the dose of Levodopa needed |
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Effectiveness of the Levodopa & Carbidopa combination?
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- Substantially reduce the severity of the disease for the first few years of treatment
- Patients will typically decline in response during the 3rd-5th years |
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Non-specific MAO Inhibitors and Levodopa
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Can produce a hypertensive crisis
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Antipsychotic drugs and Parkinson disease
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Contraindicated because they block Dopamine receptors and can produce a Parkinsonian syndrome
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What is the mechanism of action for Selegiline?
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It is a selective MAO B Inhibitor which prevents the metabolism of Dopamine
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What are the advantages of using Selegine?
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- It does not inhibit MAO A (which metabolizes norepinepherine)
- It leads to increased Dopamine levels in the brain - It significantly reduces the required dose of Levodopa - Unless it is in extremely high doses, it does not cause hypertensive crises |
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What are the two COMT Inhibitors currently used in the treatment of Parkinson disease?
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Entacapone and Tolcapone
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How are COMT Inhibitors used in the treatment of Parkinson disease?
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- They reduce the competitive metabolites produced in the periphery by Carbidopa
- This allows more Levodopa to cross the BBB without competition - This reduces the "wearing-off" phenomenon seen in Levodopa-Carbadopa patients |
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- What is the more widely accepted COMT Inhibitor nowadays?
- Why? |
- Entacapone
- Because Tolcapone has the adverse effect of causing fulminating hepatic necrosis, which required extensive hepatic monitoring |
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Ergotamine-derived Dopamine receptor agonists
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Bromocriptine and Pergolide
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Adverse effects of the Ergotamine-derived Dopamine receptor agonists
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- Vasoconstrictor action - causing pulmonary and retroperitoneal fibrosis
- Hallucinations, confusion, delirium, nausea, orthostatic hypotension - Can exacerbate psychiatric illness - Worsening of vasospasm in PAD/PVD |
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Non-ergot Dopamine agonists
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Pramipexole and Ropinirole
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Benefits of the Non-ergot Dopamine agonists
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- In early Parkinson - may delay the need to employ Levodopa
- In late Parkinson - may reduce the dose of Levodopa - Do not exacerbate vasospasm in PAD/PVD - Do not cause pulmonary or retroperitoneal fibrosis |
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Amantadine
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- Normally used as an antiviral drug used in the treatment of influenza
- Also has an antiparkinsonian effect |
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Disadvantages of Amantadine use in the treatment of Parkinson disease
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- Less efficacious than Levodopa
- Tolerance develops more readily - Little effect on tremors |
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Effectiveness of Amantadine use in the treatment of Parkinson disease
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- Has an antiparkisonian effect
- More effective than the anticholinergics against rigidity and bradykinesia |
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Antimuscarinic drugs used in the treatment of Parkinson disease
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Benztropine and Trihexyphenidyl
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Disadvantages of the Antimuscarinic drugs
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- Mood changes, xerostomia, visual problems
- Counter-indicated in patients with glaucoma and prostatic hypertrophy - Adverse effects similar to that seen with Atropine: pupillary dilation, urinary retention, dry mouth |
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Acetylcholinesterase Inhibitors used in the treatment of Alzheimer disease
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Donepezil, Galantamine, and Rivastigmine
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