Parkinsonism and Parkinson's Disease Overview
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Questions and Answers

What is a potential side effect of using selegiline with levodopa?

  • Nausea (correct)
  • Hypertension
  • Diarrhoea (correct)
  • Hypersensitivity
  • Why is tolcapone's use restricted in Europe and Canada?

  • It causes chronic insomnia.
  • It is ineffective for Parkinson's disease.
  • It has been associated with acute fatal hepatitis. (correct)
  • It leads to severe respiratory depression.
  • Which medication is known to interact with pethidine, enhancing its effects?

  • Entacapone
  • Rasagiline
  • Tolcapone
  • Selegiline (correct)
  • Which of the following is a characteristic of Rasagiline compared to selegiline?

    <p>Longer acting (B)</p> Signup and view all the answers

    What is the recommended dose for entacapone when taken with levodopa-carbidopa?

    <p>200 mg with each dose (A)</p> Signup and view all the answers

    What type of drug is selegiline classified as?

    <p>MAO-B inhibitor (D)</p> Signup and view all the answers

    What is a prominent side effect reported in patients taking tolcapone?

    <p>Diarrhoea (A)</p> Signup and view all the answers

    Which of the following statements is true regarding entacapone?

    <p>It helps reduce off time when administered with levodopa. (D)</p> Signup and view all the answers

    What is one of the therapeutic effects of ropinirole in patients with Parkinson's disease?

    <p>Decreases the 'wearing off' effect of levodopa (B)</p> Signup and view all the answers

    What common side effect should patients be cautioned about when taking ropinirole?

    <p>Nausea and dizziness (B)</p> Signup and view all the answers

    How does pramipexole compare to ropinirole in terms of potency?

    <p>It is twice as potent as ropinirole. (C)</p> Signup and view all the answers

    What should patients taking higher doses of ropinirole be cautious of?

    <p>Hypertensive interactions with levodopa (B)</p> Signup and view all the answers

    What may worsen in advanced cases when taking pramipexole?

    <p>Peak dose levodopa side effects (B)</p> Signup and view all the answers

    What is the starting dose of ropinirole in managing restless leg syndrome?

    <p>0.25 mg TDS (A)</p> Signup and view all the answers

    What is the effect of selegiline when administered with levodopa?

    <p>Prolongs levodopa action and attenuates motor fluctuations (C)</p> Signup and view all the answers

    What is a potential side effect of pramipexole?

    <p>Visual hallucinations (C)</p> Signup and view all the answers

    What is the primary effect of dopaminergic action in the striatum regarding SN-PR and GP-I?

    <p>Inhibitory influence (B)</p> Signup and view all the answers

    How does levodopa affect prolactin levels during therapy?

    <p>Decreases prolactin levels (A)</p> Signup and view all the answers

    What physiological process affects the bioavailability of levodopa?

    <p>Gastric emptying speed (D)</p> Signup and view all the answers

    What condition results from the degenerative lesion in SN-PC in Parkinson’s disease?

    <p>Imbalance between dopamine and acetylcholine (A)</p> Signup and view all the answers

    What major neurotransmitter actions are inhibited by endocrine dopamine on pituitary mamotropes?

    <p>Inhibits prolactin release (D)</p> Signup and view all the answers

    What role does the GABAergic link play in the output from SN-PR and GP-I?

    <p>Inhibitory feedback (C)</p> Signup and view all the answers

    Which neurotransmitter is primarily affected by therapeutic doses of levodopa in Parkinson’s patients?

    <p>Acetylcholine (A)</p> Signup and view all the answers

    What is one of the side effects commonly experienced by patients undergoing therapy with levodopa?

    <p>Nausea and vomiting (A)</p> Signup and view all the answers

    What is the primary symptom improvement observed in parkinsonian patients treated with levodopa?

    <p>Reduced rigidity (D)</p> Signup and view all the answers

    What effect does excess dopamine (DA) and norepinephrine (NA) formed in the brain have on sympathetic outflow?

    <p>Reduces sympathetic outflow (D)</p> Signup and view all the answers

    Which secondary symptoms gradually normalize with treatment using levodopa?

    <p>Mood and interest in life (B)</p> Signup and view all the answers

    How is the therapeutic benefit of levodopa affected as the disease advances in parkinsonian patients?

    <p>It declines (D)</p> Signup and view all the answers

    What kind of receptors are present in the Chemoreceptor Trigger Zone (CTZ) and how does dopamine (DA) function there?

    <p>Dopaminergic, acting as an excitatory transmitter (B)</p> Signup and view all the answers

    What type of pathways do striatal GABAergic neurons follow to interact with the basal ganglia?

    <p>Direct and indirect pathways (B)</p> Signup and view all the answers

    What gradual effect does levodopa have on the cardiovascular system?

    <p>Develops tolerance to hypotensive actions (A)</p> Signup and view all the answers

    What is the primary neurotransmitter action in the direct pathway modulated by D1 receptors?

    <p>Excitatory action (D)</p> Signup and view all the answers

    What is a common side effect associated with high doses of bromocriptine?

    <p>Nausea and vomiting (A)</p> Signup and view all the answers

    Which of the following symptoms may worsen when using bromocriptine?

    <p>Involuntary movements (A)</p> Signup and view all the answers

    What are the newer D2/D3 receptor agonists mentioned as alternatives to bromocriptine?

    <p>Ropinirole and Pramipexole (C)</p> Signup and view all the answers

    When combining levodopa with carbidopa, what is the name given to this combination?

    <p>Co-careldopa (A)</p> Signup and view all the answers

    What potential issue can arise with the 'first dose' of medications that lower blood pressure?

    <p>Marked fall in blood pressure (D)</p> Signup and view all the answers

    Which of the following statements about levodopa is true?

    <p>Levodopa is generally combined with a decarboxylase inhibitor. (A)</p> Signup and view all the answers

    What does excessive daytime sleepiness indicate in some patients?

    <p>Potential side effects of treatment (A)</p> Signup and view all the answers

    What is the initial dosage of bromocriptine recommended for use at night?

    <p>1.25 mg once at night (C)</p> Signup and view all the answers

    What was amantadine originally developed for?

    <p>Prophylaxis of influenza A2 (B)</p> Signup and view all the answers

    What is the role of COMT inhibitors like entacapone and tolcapone in Parkinson's disease therapy?

    <p>They prolong the half-life of levodopa. (D)</p> Signup and view all the answers

    Which property of amantadine contributes to its benefits in parkinsonism?

    <p>Antagonism of NMDA receptors (A)</p> Signup and view all the answers

    What happens to the efficacy of levodopa when combined with carbidopa and COMT inhibitors over time?

    <p>Tolerance develops and efficacy is gradually lost. (A)</p> Signup and view all the answers

    Which statement is true regarding the action of entacapone?

    <p>It mainly affects peripheral pathways. (C)</p> Signup and view all the answers

    Which group of patients is most likely to benefit from amantadine?

    <p>Patients with mild cases or those with advanced disease (B)</p> Signup and view all the answers

    What effect does COMT have on dopamine in the brain?

    <p>It enhances the degradation of dopamine. (D)</p> Signup and view all the answers

    Why might amantadine be considered less efficacious compared to levodopa?

    <p>Amantadine is not a dopamine agonist. (D)</p> Signup and view all the answers

    Flashcards

    Levodopa

    A medication used to treat Parkinson's disease by increasing dopamine levels in the brain.

    Carbidopa

    A medication used to treat Parkinson's disease that prevents the breakdown of levodopa, increasing its effectiveness.

    Co-careldopa

    A combination of levodopa and carbidopa, often used to treat Parkinson's disease.

    Dyskinesia

    Involuntary movements, especially in the limbs, that can occur as a side effect of levodopa treatment.

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    Bromocriptine

    A dopamine agonist medication used to treat Parkinson's disease.

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    Non-ergot dopamine agonists

    Dopamine receptor agonists that are not based on the ergot molecule.

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    Ropinirole

    A non-ergot dopamine agonist used to treat Parkinson's disease.

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    Pramipexole

    A non-ergot dopamine agonist used to treat Parkinson's disease.

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    Levodopa's effect on healthy individuals

    Levodopa is ineffective in healthy individuals or patients with other neurological conditions, but provides significant improvement in symptoms of Parkinson's disease.

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    Order of symptom improvement with Levodopa

    Symptoms like hypokinesia and rigidity improve first, followed by tremor, indicating a gradual restoration of movement control.

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    Levodopa's effects on secondary symptoms

    Levodopa's positive effects on posture, gait, handwriting, speech, facial expressions, mood, and overall well-being gradually normalize as the treatment progresses.

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    Levodopa's effectiveness over time

    Levodopa's therapeutic benefits are most pronounced in the early stages of Parkinson's disease but gradually diminish as the disease advances.

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    Levodopa's effect on behavior

    Levodopa's overall effect can be described as a ‘general alerting response’, improving alertness and overall cognitive function.

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    Levodopa's side effects: Nausea & Vomiting

    Levodopa's conversion to dopamine in the periphery can lead to side effects like nausea and vomiting.

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    Levodopa's side effects: Postural Hypotension

    Levodopa can cause postural hypotension due to a decrease in sympathetic outflow and DA's action on autonomic ganglia. Tolerance develops over time.

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    Levodopa's action on the CTZ

    Dopaminergic receptors in the chemoreceptor trigger zone (CTZ) are stimulated by dopamine, leading to nausea and vomiting. Tolerance develops gradually.

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    MAO-B Inhibitors

    A class of drugs that inhibit the enzyme monoamine oxidase type B (MAO-B). MAO-B breaks down dopamine, a neurotransmitter important for movement. Inhibiting MAO-B increases dopamine levels, which can help improve symptoms of Parkinson's disease.

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    Selegiline

    A type of MAO-B inhibitor used to treat Parkinson's disease. It is given twice a day and can be used alone in early stages or with levodopa/carbidopa in later stages.

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    Rasagiline

    A newer MAO-B inhibitor with similar effects to selegiline but with a longer duration of action and is given only once a day.

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    COMT Inhibitors

    Drugs that block the enzyme catechol-o-methyltransferase (COMT). COMT breaks down levodopa, a medication used to treat Parkinson's disease, before it can reach the brain. Blocking COMT allows more levodopa to reach the brain and improve symptoms.

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    Entacapone

    A commonly used COMT inhibitor, taken with each dose of levodopa/carbidopa. It helps improve efficacy of levodopa.

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    Tolcapone

    A COMT inhibitor with a stronger effect than entacapone, but its use is restricted due to potential side effects like liver damage.

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    NMDA Receptor

    A type of receptor in the brain that is involved in regulating the release of dopamine. Blocking NMDA receptors can help increase dopamine levels and improve symptoms of Parkinson's disease.

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    NMDA Receptor Antagonists

    Drugs that block the NMDA receptor. This can help facilitate dopamine release, leading to improvement in Parkinson's symptoms.

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    Amantadine's unexpected benefit

    Amantadine, initially an antiviral drug, was unexpectedly found to improve Parkinson's symptoms.

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    COMT inhibitors in Parkinson's

    COMT inhibitors like Entacapone and Tolcapone are used alongside levodopa to enhance its effects in advanced Parkinson's disease.

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    How do COMT inhibitors work?

    Entacapone and Tolcapone block COMT, an enzyme that breaks down levodopa, allowing more levodopa to reach the brain.

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    How does Amantadine work in Parkinson's?

    Amantadine improves Parkinson's symptoms by promoting dopamine release and acting as an anticholinergic, but its most significant effect is likely through blocking NMDA receptors.

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    When is Amantadine used?

    Amantadine can be used for milder Parkinson's cases, or in short bursts to manage fluctuations in advanced cases.

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    Peripheral vs. central COMT action

    COMT inhibitors primarily act on the periphery, with limited central effects, while dopamine is broken down in both the periphery and the brain.

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    Carbidopa and benserazide's role

    Carbidopa and benserazide are medications used to prevent levodopa breakdown in the periphery, allowing more of it to reach the brain.

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    Amantadine's tolerance

    Amantadine's efficacy in Parkinson's gradually decreases over time due to tolerance development.

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    Dopamine Agonist

    A type of medication used to treat Parkinson's disease. It works by mimicking dopamine's action in the brain, helping to improve movement and coordination. It is longer acting than levodopa and can help manage motor fluctuations and reduce the frequency of "on-off" effects.

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    "On-off" Effects

    A type of side effect experienced by some individuals taking dopamine agonists, characterized by unpredictable fluctuations in motor symptoms or medication response. This often leads to a 'on' state (good control) and an 'off' state (worse symptoms) in individuals with Parkinson's disease.

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    Daytime Sleepiness

    A common side effect of dopamine agonists that can disrupt a person's sleep patterns, making them feel excessively sleepy during the day.

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    Postural Hypotension

    A common side effect of dopamine agonists characterized by a sudden drop in blood pressure when standing up, leading to dizziness or lightheadedness.

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    MAO-B Inhibitor (Selegiline)

    A type of medication that inhibits the breakdown of dopamine in the brain, leading to increased dopamine levels. It acts as an adjunct to levodopa therapy in Parkinson's disease, prolonging the duration of action and potentially reducing side effects.

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    Hallucinations

    A common side effect of dopamine agonists that can be distressing, characterized by seeing or hearing things that aren't real. It can be more common in individuals with Parkinson's disease and may affect their quality of life.

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    What is the function of the basal ganglia?

    The basal ganglia's primary role is to fine-tune motor control, balancing excitatory and inhibitory signals to produce smooth, coordinated movements. It helps reduce involuntary movements known as muscle tone, ensuring efficient and controlled motor output.

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    How does Parkinson's disease affect the basal ganglia?

    In Parkinson's disease, the degeneration of dopamine-producing cells in the substantia nigra disrupts the balance between dopamine and acetylcholine in the striatum, leading to a decrease in motor activity and the development of rigidity, tremors, and hypokinesia.

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    Describe the pharmacokinetics of Levodopa.

    Levodopa, a precursor to dopamine, is rapidly absorbed from the small intestine. It utilizes the same transport system as other aromatic amino acids, but its bioavailability is affected by factors like gastric emptying speed and competition from other amino acids in food.

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    How does gastric emptying rate affect Levodopa bioavailability?

    Levodopa's absorption rate can be affected by gastric emptying rate. Slow emptying increases the time Levodopa spends in the gut, exposing it to degrading enzymes and reducing its availability to reach the brain.

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    How do amino acids in food affect Levodopa absorption?

    The active transport system for Levodopa absorption can be hindered by other amino acids present in food. This competition reduces Levodopa's uptake into the bloodstream.

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    What is meant by Levodopa's 'first-pass metabolism'?

    Levodopa undergoes a significant first-pass metabolism in the gut and liver. This means a large portion of the drug is metabolized before it reaches the bloodstream, affecting its bioavailability.

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    What are some common side effects of Levodopa therapy?

    Common side effects of Levodopa therapy include nausea, vomiting, and involuntary movements. Starting with a low dose and gradually increasing it can minimize these side effects.

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    How does nausea and vomiting typically respond to Levodopa therapy?

    Initially, patients often experience nausea and vomiting during Levodopa therapy. However, tolerance to these side effects usually develops over time, allowing for dose increases.

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    Study Notes

    Parkinsonism

    • Parkinsonism is an extrapyramidal motor disorder, characterized by rigidity, tremor and hypokinesia
    • Secondary manifestations include posture and gait problems, a mask-like face, and excessive saliva.
    • Dementia may accompany the condition.
    • Untreated symptoms can progress over years, leading to severe rigidity, immobility, breathing issues, and susceptibility to infections or embolism.

    Parkinson's Disease (PD)

    • PD is a progressive degenerative disorder, primarily affecting older individuals.
    • Idiopathic cases are most common, some may be related to arteriosclerosis, and postencephalitic cases are rare.
    • Wilson's disease, a rare copper poisoning disorder, can be a cause.
    • The primary pathological lesion is the degeneration of substantia nigra pars compacta (SN-PC) neurons and the nigrostriatal dopaminergic tract.
    • This leads to reduced dopamine (DA) in the striatum, impacting muscle tone and movement coordination.
    • An imbalance arises between dopaminergic and cholinergic systems.
    • The exact cause of the neuronal degeneration is uncertain, but it likely involves multiple factors like oxidation of DA by MAO-B and aldehyde dehydrogenase, leading to free radical formation, age-related or acquired defects in protective mechanisms, mitochondrial dysfunction, and potential environmental toxins or genetic factors.

    Antiparkinsonian Drugs

    • These drugs effectively treat symptoms of parkinsonism.
    • Levodopa was a significant breakthrough in 1967 for its role in restoring dopamine levels.
    • DA itself cannot cross the blood-brain barrier, so Levodopa (a precursor) is used.
    • Drugs are classified into ones impacting the brain's dopaminergic system:
      • Dopamine precursor: Levodopa (l-dopa)
      • Peripheral decarboxylase inhibitors: Carbidopa, Benserazide.
      • Dopaminergic agonists: Bromocriptine, Ropinirole, Pramipexole.
      • MAO-B inhibitor: Selegiline, Rasagiline
      • COMT inhibitors: Entacapone, Tolcapone.

    Drug Actions

    • Levodopa has a specific beneficial effect in PD, outperforming other treatments.
    • It's inactive by itself, acting as a precursor to DA.
    • Peripheral metabolism degrades over 95% of an oral levodopa dose.
    • DA formed crosses the blood-brain barrier.
    • Levodopa can improve hypokinesia, rigidity, and tremor, impacting posture, gait, and speech.

    Classification of Drugs

    • Drugs affecting brain cholinergic system:
      • Central anticholinergics: Trihexyphenidyl, Procyclidine, Biperiden.
      • Antihistaminics: Orphenadrine, Promethazine

    Levodopa adverse effects

    • Early effects: nausea, vomiting, postural hypotension.
    • Long-term effects: dyskinesias (abnormal movements), behavioural changes (depression, psychosis), and fluctuations in motor control (on-off phenomenon).

    Dopamine agonists

    • Act on DA receptors, even in advanced PD.
    • Bromecriptine, a potent D2 agonist, is used in advanced cases.
    • Ropinirole and Pramipexole are newer, non-ergot DA agonists, preferred for their tolerability and reduced risk of long-term side effects.

    MAO-B inhibitors

    • Selegiline (Deprenyl) is a selective MAO-B inhibitor.
    • Used in early PD cases and with Levodopa to improve symptoms, extend 'on' time and reduce motor fluctuations.
    • Rasagiline is a newer MAO-B inhibitor, potentially slowing neuronal degeneration.

    COMT inhibitors

    • Entacapone and Tolcapone enhance levodopa's action in advanced and fluctuating PD.
    • Tolcapone has a higher incidence of side effects (hepatitis).
    • Increasing 'on' time, decreasing 'off' time, improving daily living activities, and reducing levodopa dose are potential benefits.

    Other drugs

    • Amantadine acts as a glutamate NMDA receptor antagonist, offering additional benefits and acting to maintain and enhance levodopa effectiveness, particularly in milder cases.
    • Central anticholinergics
      • Improve symptoms, particularly tremor, in early PD.
      • Commonly used drug is Trihexyphenidyl.
      • Not as effective as levodopa and have more side effects.

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    This quiz examines the characteristics and pathology of Parkinsonism and Parkinson's Disease (PD). It covers the symptoms, progression, and underlying neurological changes associated with these conditions. Test your knowledge on the causes and effects of this neurodegenerative disorder.

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