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Questions and Answers
Which of the following drugs is classified as a dopamine receptor agonist used in the treatment of Parkinson’s disease?
Which of the following drugs is classified as a dopamine receptor agonist used in the treatment of Parkinson’s disease?
- Pramipexole (correct)
- Comtan
- Benserazide
- Memantine
What is a common adverse effect of L-dopa treatment in Parkinson’s disease?
What is a common adverse effect of L-dopa treatment in Parkinson’s disease?
- Cognitive impairment
- Tardive dyskinesia
- Nausea (correct)
- Severe hypertension
Which class of drugs used in Parkinson’s disease works by preventing dopamine degradation?
Which class of drugs used in Parkinson’s disease works by preventing dopamine degradation?
- MAO-B inhibitors (correct)
- Dopamine releasing agents
- Anticholinergics
- COMT inhibitors
What is the primary action of carbidopa and benserazide when used with L-dopa?
What is the primary action of carbidopa and benserazide when used with L-dopa?
Which of the following is an NMDA receptor antagonist used in Alzheimer's disease treatment?
Which of the following is an NMDA receptor antagonist used in Alzheimer's disease treatment?
Which drug is NOT commonly used in Huntington’s chorea?
Which drug is NOT commonly used in Huntington’s chorea?
How do centrally acting anticholinergics help in drug-induced parkinsonism?
How do centrally acting anticholinergics help in drug-induced parkinsonism?
Which of the following is a decarboxylase inhibitor used with L-dopa?
Which of the following is a decarboxylase inhibitor used with L-dopa?
What is the role of COMT inhibitors in Parkinson’s disease therapy?
What is the role of COMT inhibitors in Parkinson’s disease therapy?
What is the primary action of centrally acting anticholinergics in the treatment of drug-induced parkinsonism?
What is the primary action of centrally acting anticholinergics in the treatment of drug-induced parkinsonism?
Which symptom is most effectively managed by centrally acting anticholinergics like benztropine?
Which symptom is most effectively managed by centrally acting anticholinergics like benztropine?
Why are other anti-parkinsonian drugs not effective in treating drug-induced parkinsonism?
Why are other anti-parkinsonian drugs not effective in treating drug-induced parkinsonism?
What peripheral symptom is controlled by the action of centrally acting anticholinergics?
What peripheral symptom is controlled by the action of centrally acting anticholinergics?
Which of the following is a major limitation of using dopamine receptor agonists in drug-induced parkinsonism?
Which of the following is a major limitation of using dopamine receptor agonists in drug-induced parkinsonism?
When treating drug-induced parkinsonism, which class of medication is predominantly preferred?
When treating drug-induced parkinsonism, which class of medication is predominantly preferred?
What percentage of levodopa crosses the blood-brain barrier (BBB)?
What percentage of levodopa crosses the blood-brain barrier (BBB)?
What is the primary role of carbidopa in combination therapy with levodopa?
What is the primary role of carbidopa in combination therapy with levodopa?
Which of the following is a limitation of the carbidopa and levodopa combination?
Which of the following is a limitation of the carbidopa and levodopa combination?
What is the end product of catechol-O-methyl transferase (COMT) mediated degradation of levodopa?
What is the end product of catechol-O-methyl transferase (COMT) mediated degradation of levodopa?
Which enzyme do COMT inhibitors primarily inhibit to enhance the effects of levodopa?
Which enzyme do COMT inhibitors primarily inhibit to enhance the effects of levodopa?
What is one effect of the combination of carbidopa and levodopa on levodopa dose requirements?
What is one effect of the combination of carbidopa and levodopa on levodopa dose requirements?
What effect does selegiline have in the treatment of Parkinson's disease?
What effect does selegiline have in the treatment of Parkinson's disease?
What adverse effect is NOT resolved by the combination of carbidopa and levodopa?
What adverse effect is NOT resolved by the combination of carbidopa and levodopa?
Which pathway does levodopa take after being converted in the brain due to the combination with carbidopa?
Which pathway does levodopa take after being converted in the brain due to the combination with carbidopa?
What happens to the systemic concentration of dopamine with the combination of carbidopa and levodopa?
What happens to the systemic concentration of dopamine with the combination of carbidopa and levodopa?
What is the primary function of levodopa in the treatment of Parkinson's disease?
What is the primary function of levodopa in the treatment of Parkinson's disease?
What peripheral adverse effect can occur due to the agonistic action of dopamine on the DA receptor in the CTZ?
What peripheral adverse effect can occur due to the agonistic action of dopamine on the DA receptor in the CTZ?
What phenomenon describes the rapid fluctuation in the efficacy of levodopa in patients?
What phenomenon describes the rapid fluctuation in the efficacy of levodopa in patients?
Which of the following is a potential CNS adverse effect of levodopa?
Which of the following is a potential CNS adverse effect of levodopa?
How does pyridoxine (Vitamin B6) interact with levodopa?
How does pyridoxine (Vitamin B6) interact with levodopa?
What effect can levodopa have on patients with existing heart conditions?
What effect can levodopa have on patients with existing heart conditions?
What is one of the common movements associated with dyskinesias due to levodopa?
What is one of the common movements associated with dyskinesias due to levodopa?
Which of the following describes a tolerance effect that may occur with prolonged levodopa treatment?
Which of the following describes a tolerance effect that may occur with prolonged levodopa treatment?
What is the mechanism of action of carbidopa in combination with levodopa?
What is the mechanism of action of carbidopa in combination with levodopa?
What is a significant reason for the wearing-off effect in patients on levodopa therapy?
What is a significant reason for the wearing-off effect in patients on levodopa therapy?
What is the primary mechanism by which amantadine provides symptomatic relief in parkinsonism?
What is the primary mechanism by which amantadine provides symptomatic relief in parkinsonism?
Which of the following actions does selegiline NOT possess?
Which of the following actions does selegiline NOT possess?
Dopamine agonists are particularly useful in which situation?
Dopamine agonists are particularly useful in which situation?
What additional effect does amantadine have beyond facilitating dopamine release?
What additional effect does amantadine have beyond facilitating dopamine release?
The rationale for using centrally acting anticholinergics in drug-induced parkinsonism involves which mechanism?
The rationale for using centrally acting anticholinergics in drug-induced parkinsonism involves which mechanism?
Which dopamine receptor agonist is known for having a longer duration of action compared to levodopa?
Which dopamine receptor agonist is known for having a longer duration of action compared to levodopa?
What effect does drug-induced parkinsonism primarily occur through?
What effect does drug-induced parkinsonism primarily occur through?
Which of the following properties is NOT associated with dopamine receptor agonists?
Which of the following properties is NOT associated with dopamine receptor agonists?
How does selegiline contribute to the management of Parkinson’s disease?
How does selegiline contribute to the management of Parkinson’s disease?
What is a common effect of both amantadine and dopamine agonists in treating parkinsonism?
What is a common effect of both amantadine and dopamine agonists in treating parkinsonism?
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Study Notes
Drug Therapy of Neurodegenerative Disorders
- Parkinson’s Disease Drug Classification:
- Dopamine level increasers:
- Levodopa (dopamine precursor)
- Carbidopa and Benserazide (decarboxylase inhibitors)
- Tolcapone and Entacapone (COMT inhibitors)
- Amantadine (dopamine releasing agent)
- Dopamine degradation preventers:
- Selegiline and Rasagiline (MAO-B inhibitors)
- Dopamine receptor agonists:
- Bromocriptine, Cabergoline, Ropinirole, Pramipexole
- DA-ACh balance restorers:
- Benztropine and Benzhexol (centrally acting anticholinergics)
- Dopamine level increasers:
Alzheimer's Disease and Huntington's Chorea Drugs
- Alzheimer’s Disease:
- Anticholinesterases: Donepezil, Rivastigmine, Galantamine
- NMDA receptor antagonist: Memantine
- Huntington’s Chorea:
- Chlorpromazine, Haloperidol, Olanzapine, Tetrabenazine
Adverse Effects of Levodopa
- Peripheral Effects:
- Nausea and vomiting due to dopamine stimulation in CTZ
- Arrhythmias from beta receptor agonism
- Postural hypotension, altered taste and smell
- CNS Effects:
- Fluctuations: Wearing-off and on-off phenomena
- Dyskinesias: Abnormal movements (tics, tremors)
- Psychiatric symptoms: Hallucinations, confusion, insomnia
Drug Interaction: Levodopa and Pyridoxine
- Pyridoxine enhances peripheral decarboxylase activity, increasing levodopa metabolism before crossing the BBB and diminishing its therapeutic effects.
Benefits of Levodopa and Carbidopa Combination
- Maximizes levodopa crossing into the brain, allowing for better dopamine levels.
- Prolonged plasma half-life and increased bioavailability of dopamine in the brain.
- Significant reduction in levodopa dosage, minimizing peripheral side effects.
- Helps maintain stable dopamine levels, reducing the on-off effect.
Limitations of Levodopa and Carbidopa Combination
- Does not eliminate postural hypotension.
- May exacerbate involuntary movements and behavioral abnormalities.
Antiparkinsonian Actions of Various Drugs
- COMT Inhibitors (e.g., Tolcapone):
- Prevent peripheral degradation of levodopa, enhancing dopamine delivery to the brain.
- MAO-B Inhibitors (e.g., Selegiline):
- Inhibit MAO-B to increase dopamine levels and provide neuroprotective effects.
- Amantadine:
- Increases presynaptic DA release and inhibits DA reuptake, also has weak antimuscarinic effects.
- Dopamine Agonists:
- Stimulate postsynaptic dopamine receptors directly, beneficial for advanced parkinsonism with less risk of dyskinesias.
Centrally Acting Anticholinergics in Drug-Induced Parkinsonism
- Used to rebalance cholinergic activity when dopamine receptors are blocked (e.g., by Metoclopramide).
- Drugs like Benztropine and Benzhexol target muscarinic receptors in the basal ganglia, effectively reducing tremors and rigidity.
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