Antiparkinsonian Drugs — MCQs
Which of the following drugs is primarily used for the treatment of Parkinson's disease?
A 50-year-old with Parkinson's disease is on levodopa. Adding which drug helps manage 'wearing-off' effects?
What is the treatment for extrapyramidal side effects induced by Haloperidol?
Which antipsychotic drug is approved for the management of psychosis in Parkinsonian patients?
A 65-year-old woman with Parkinson’s disease has been experiencing worsening tremors despite taking levodopa. Which medication can be added to her treatment regimen?
Which of the following antiepileptic drugs is preferred for treating generalized tonic-clonic seizures?
According to traditional teaching, dopamine is preferred over dobutamine in treatment of renal shock because:
Which medication is used for suppression of lactation?
A 68-year-old with depression and chronic pain is on amitriptyline. What side effect may arise if given oxybutynin for overactive bladder?
A 25-year-old woman going on a luxury holiday cruise has motion sickness. She is prescribed this transdermal scopolamine delivery patch. All are true about its usage except:
Antiparkinsonian Drugs Indian Medical PG Practice Questions and MCQs
Question 1: Which of the following drugs is primarily used for the treatment of Parkinson's disease?
- A. Mazindol
- B. Benserazide
- C. Levodopa (Correct Answer)
- D. Bromocriptine
Explanation: ***Levodopa*** - Levodopa is a **dopamine precursor** that crosses the blood-brain barrier and is converted to dopamine in the brain, replacing the depleted dopamine in Parkinson's disease [1], [2]. - It is considered the **most effective drug** for managing the motor symptoms of Parkinson's disease, particularly in the early and moderate stages [2], [4]. *Mazindol* - **Mazindol** is an appetite suppressant used for obesity and acts primarily as a norepinephrine-dopamine reuptake inhibitor. - It is **not indicated** for the treatment of Parkinson's disease. *Benserazide* - **Benserazide** is a **peripheral DOPA decarboxylase inhibitor** that does not cross the blood-brain barrier [1]. - It is used in combination with levodopa (e.g., in co-beneldopa) to prevent the peripheral metabolism of levodopa, increasing its availability to the brain, but it is **not used alone** to treat Parkinson's disease [1]. *Bromocriptine* - **Bromocriptine** is a **dopamine agonist** that directly stimulates dopamine receptors in the brain [3]. - While used in Parkinson's disease, it is generally considered a **second-line treatment** or used as an adjunct to levodopa, and not the primary drug [3].
Question 2: A 50-year-old with Parkinson's disease is on levodopa. Adding which drug helps manage 'wearing-off' effects?
- A. Entacapone (Correct Answer)
- B. Amantadine
- C. Selegiline
- D. Bromocriptine
Explanation: ***Entacapone*** - **Entacapone** is a **COMT inhibitor** that prolongs the action of **levodopa** in the brain by preventing its peripheral breakdown. - This effectively reduces the "wearing-off" phenomenon, where the effects of levodopa diminish before the next dose. *Amantadine* - **Amantadine** is primarily used to treat **dyskinesias** associated with long-term levodopa therapy in Parkinson's disease. - While it has some dopaminergic activity, it is not the primary choice for managing **"wearing-off" fluctuations**. *Selegiline* - **Selegiline** is an **MAO-B inhibitor** that prevents the breakdown of dopamine in the brain, offering mild symptomatic benefit. - It's typically used in early Parkinson's or as an adjunct, but less effective for **"wearing-off"** compared to COMT inhibitors. *Bromocriptine* - **Bromocriptine** is a **dopamine agonist** that directly stimulates dopamine receptors. - It can be used for motor fluctuations but is more commonly associated with side effects and is generally less preferred than newer dopamine agonists for advanced Parkinson's.
Question 3: What is the treatment for extrapyramidal side effects induced by Haloperidol?
- A. Barbiturates
- B. SSRIs
- C. Benzodiazepines
- D. Anticholinergic drugs (Correct Answer)
Explanation: ***Anticholinergic drugs (effective treatment)*** - **Anticholinergic medications**, such as **benztropine** or **diphenhydramine**, are the primary treatment for **acute extrapyramidal symptoms (EPS)** like dystonia and parkinsonism induced by antipsychotics like haloperidol. - They work by **blocking muscarinic acetylcholine receptors**, helping to restore the balance between dopamine and acetylcholine in the basal ganglia. *Benzodiazepines (used for anxiety and muscle relaxation)* - While benzodiazepines can offer some relief for **akathisia** (a form of EPS characterized by restlessness) due to their sedative and muscle relaxant properties, they are **not the first-line treatment for other acute EPS** such as dystonia or parkinsonism. - They primarily enhance **GABAergic transmission** and are effective for anxiety and seizure control rather than direct antagonism of EPS mechanisms. *Barbiturates (used as sedative-hypnotic drugs)* - **Barbiturates** are strong central nervous system depressants used for sedation, anesthesia, and seizure control, but are **not indicated for the treatment of EPS**. - Their significant **sedative and addictive potential**, along with a narrow therapeutic index, makes them unsuitable for this purpose. *SSRIs (used for depression and anxiety)* - **SSRIs (Selective Serotonin Reuptake Inhibitors)** are antidepressants that work by increasing serotonin levels in the brain and are used to treat depression, anxiety, and obsessive-compulsive disorder. - They **do not have a direct role** in ameliorating dopamine-acetylcholine imbalance responsible for haloperidol-induced EPS.
Question 4: Which antipsychotic drug is approved for the management of psychosis in Parkinsonian patients?
- A. risperidone
- B. clozapine (Correct Answer)
- C. olanzapine
- D. haloperidol
Explanation: ***Correct: Clozapine*** - **Clozapine** is the only antipsychotic extensively studied and approved for the treatment of **psychosis in Parkinson's disease (PDP)** due to its low propensity to exacerbate motor symptoms. - Its unique pharmacological profile, including lower **D2 receptor blockade** compared to other antipsychotics, makes it suitable for this vulnerable population. - Clozapine has the strongest evidence base for efficacy without worsening motor function in PDP. *Incorrect: Olanzapine* - **Olanzapine** has a significant **risk of worsening motor symptoms** in Parkinson's patients due to its potent **D2 receptor antagonism**. - It is generally contraindicated for treating psychosis in Parkinson's disease. *Incorrect: Haloperidol* - **Haloperidol** is a high-potency typical antipsychotic with strong **D2 receptor blockade**, which can severely **worsen Parkinsonian motor symptoms** (e.g., rigidity, bradykinesia). - Its use is strictly avoided in patients with Parkinson's disease. *Incorrect: Risperidone* - **Risperidone** also carries a considerable risk of **exacerbating motor symptoms** in Parkinson's disease due to its **D2 receptor antagonism**, although less severe than haloperidol. - It is generally not recommended as a first-line treatment for PDP.
Question 5: A 65-year-old woman with Parkinson’s disease has been experiencing worsening tremors despite taking levodopa. Which medication can be added to her treatment regimen?
- A. Phenytoin
- B. Aspirin
- C. Ropinirole (Correct Answer)
- D. Gabapentin
Explanation: ***Ropinirole*** - **Ropinirole** is a **dopamine agonist** that directly stimulates dopamine receptors (D2 and D3) in the brain, mimicking the effects of dopamine. It is commonly used as an **adjunct to levodopa** to improve motor symptoms and reduce off-time in Parkinson's disease. - When levodopa alone is insufficient to control symptoms (as in this case), dopamine agonists like ropinirole can help to prolong the therapeutic effects and manage **motor fluctuations**, including tremors, by providing more continuous dopaminergic stimulation. - Ropinirole is FDA-approved for both **monotherapy** in early Parkinson's and as **add-on therapy** in advanced disease with motor complications. *Phenytoin* - **Phenytoin** is an **antieconvulsant** medication primarily used to treat epilepsy and certain types of seizures. - It has **no established role** in the treatment of Parkinson's disease or its associated tremors. *Aspirin* - **Aspirin** is an **NSAID** and antiplatelet agent, commonly used for pain relief, fever reduction, and cardiovascular protection. - It does **not have direct therapeutic effects** on the motor symptoms of Parkinson's disease like tremors. *Gabapentin* - **Gabapentin** is an anticonvulsant and neuropathic pain medication, often used to treat **neuropathic pain**, restless legs syndrome, and seizures. - It is **not effective** for managing the tremors or other motor symptoms of Parkinson's disease.
Question 6: Which of the following antiepileptic drugs is preferred for treating generalized tonic-clonic seizures?
- A. Ethosuximide
- B. Gabapentin
- C. Valproic acid (Correct Answer)
- D. Carbamazepine
Explanation: ***Valproic acid*** - **Valproic acid** is a broad-spectrum antiepileptic drug effective against various seizure types, including **generalized tonic-clonic seizures**. - It is considered the **gold standard** for generalized seizures because it is effective against all types (absence, myoclonic, and tonic-clonic). - It works by increasing GABA levels, blocking voltage-gated sodium channels, and inhibiting T-type calcium channels. *Ethosuximide* - **Ethosuximide** is specifically used for **absence seizures** (petit mal) and is not effective for generalized tonic-clonic seizures. - It primarily acts by blocking **T-type calcium channels** in the thalamus. *Gabapentin* - **Gabapentin** is primarily used for **focal (partial) seizures** and neuropathic pain, not generalized tonic-clonic seizures. - Its mechanism involves modulating the release of neurotransmitters, possibly by binding to the **α2δ subunit of calcium channels**. *Carbamazepine* - **Carbamazepine** is a first-line treatment for **focal (partial) seizures** and is also effective for **generalized tonic-clonic seizures**, though valproic acid is generally preferred for purely generalized seizures. - It works by blocking voltage-gated sodium channels. - It should be **avoided in absence and myoclonic seizures** as it can worsen these seizure types. - Also used for **trigeminal neuralgia**.
Question 7: According to traditional teaching, dopamine is preferred over dobutamine in treatment of renal shock because:
- A. Increased cardiac output
- B. Peripheral vasoconstriction
- C. Prolonged action
- D. Renal vasodilatory effect (Correct Answer)
Explanation: ***Renal vasodilatory effect*** - In traditional teaching, low-dose **dopamine** was thought to selectively stimulate **D1 dopamine receptors** in the kidneys, leading to **renal vasodilation** and improved renal blood flow. - This effect was believed to be beneficial in preventing or treating **acute kidney injury (AKI)** in the context of shock, thus making it a preferred agent for "renal shock." *Increased cardiac output* - While dopamine can increase **cardiac output** through beta-1 agonism at intermediate doses, dobutamine is generally considered a more potent inotropic agent for this purpose. - The primary reason for preferring dopamine in renal shock was not its inotropic effect but its purported renal-specific action. *Peripheral vasoconstriction* - At higher doses, dopamine stimulates **alpha-1 adrenergic receptors**, leading to **peripheral vasoconstriction**, which can increase **systemic vascular resistance (SVR)** and blood pressure. - This generalized vasoconstrictive effect is typically avoided in renal shock if the goal is to improve renal perfusion, as it can potentially compromise renal blood flow. *Prolonged action* - Neither dopamine nor dobutamine has a particularly **prolonged action**; both are typically administered via continuous infusion due to their short half-lives. - The duration of action was not the primary factor in preferring dopamine for renal shock.
Question 8: Which medication is used for suppression of lactation?
- A. Bromocriptine (Correct Answer)
- B. DMPA
- C. Pyridoxine
- D. D-Norgestrel
Explanation: ***Bromocriptine*** - **Bromocriptine** is a **dopamine agonist** that suppresses prolactin secretion from the anterior pituitary, thereby inhibiting lactation - Acts by stimulating **D2 dopamine receptors**, which inhibits prolactin release - Historically used for lactation suppression, though its use has declined due to potential cardiovascular side effects (**hypotension**, **stroke**, **myocardial infarction**) - **Cabergoline** (another dopamine agonist) is now preferred when pharmacological suppression is needed due to better tolerability - **Non-pharmacological methods** (breast binding, ice packs, avoiding stimulation) are now first-line recommendations *Pyridoxine* - **Pyridoxine (Vitamin B6)** has been anecdotally mentioned for lactation suppression, but lacks strong scientific evidence - Does not directly affect **prolactin secretion** or milk production mechanisms - Not recommended for this indication *DMPA* - **DMPA (Depot Medroxyprogesterone Acetate)** is a **progestin-only injectable contraceptive** used postpartum - Safe for breastfeeding mothers as its primary function is **contraception**, not lactation suppression - Does not actively suppress established lactation *D-Norgestrel* - **D-Norgestrel** is a **progestin** component found in some oral contraceptive pills - Primary role is **contraception**, not lactation suppression - Progestin-only contraceptives are compatible with breastfeeding
Question 9: A 68-year-old with depression and chronic pain is on amitriptyline. What side effect may arise if given oxybutynin for overactive bladder?
- A. Severe dry mouth (Correct Answer)
- B. Bradycardia
- C. Increased sweating
- D. Urinary incontinence
Explanation: ***Severe dry mouth*** - Both **amitriptyline** (a tricyclic antidepressant) and **oxybutynin** (an anticholinergic for overactive bladder) have significant anticholinergic effects. - The combination of these two drugs can lead to an additive effect, causing pronounced anticholinergic side effects such as **severe dry mouth**, blurred vision, constipation, and cognitive impairment. *Bradycardia* - **Anticholinergic drugs** typically cause **tachycardia** (increased heart rate) by blocking the parasympathetic nervous system's muscarinic receptors on the heart, rather than bradycardia. - While amitriptyline can affect cardiac conduction, severe bradycardia is not a typical **additive anticholinergic side effect** in this context. *Increased sweating* - **Anticholinergic drugs** like amitriptyline and oxybutynin inhibit the activity of sweat glands, which are primarily innervated by cholinergic nerves. - Therefore, the combination of these drugs would likely lead to **decreased sweating** (anhidrosis) rather than increased sweating. *Urinary incontinence* - **Oxybutynin** is prescribed specifically to treat **overactive bladder** and reduce urinary incontinence by relaxing the detrusor muscle. - Therefore, it would improve rather than worsen urinary incontinence; however, it can cause **urinary retention** due to its anticholinergic effect, especially in older male patients.
Question 10: A 25-year-old woman going on a luxury holiday cruise has motion sickness. She is prescribed this transdermal scopolamine delivery patch. All are true about its usage except:
- A. Postauricular hairless skin has best delivery
- B. Contact with the exposed adhesive layer should be avoided to prevent contamination of fingers with scopolamine
- C. Slow absorption with lack of first pass metabolism
- D. Remove patch immediately if there is pupil constriction and sialorrhea (Correct Answer)
Explanation: ***Remove patch immediately if there is pupil constriction and sialorrhea*** - Scopolamine is an **anticholinergic drug**; its side effects typically include **mydriasis (pupil dilation)** and **xerostomia (dry mouth)**, not constriction and increased salivation. - Therefore, pupil constriction and sialorrhea are **not expected adverse effects** of scopolamine and would not be a reason to immediately remove the patch based on its direct pharmacological action. *Postauricular hairless skin has best delivery* - The **postauricular area (behind the ear)** is a common and recommended site for scopolamine patch application due to its relatively thin, hairless skin and good blood supply, facilitating consistent drug absorption. - This location minimizes interference from hair and movement, which could dislodge the patch or affect absorption. *Contact with the exposed adhesive layer should be avoided to prevent contamination of fingers with scopolamine* - Directly touching the adhesive side of the patch can **transfer scopolamine** to the fingers, potentially leading to systemic absorption if the fingers are then brought to the eyes or mouth. - Accidental systemic absorption can cause side effects like **mydriasis** or **dry mouth** even if the patch is correctly applied elsewhere. *Slow absorption with lack of first-pass metabolism* - Transdermal patches deliver medication directly into the bloodstream, bypassing the **liver's first-pass metabolism**. - This results in a **slower, more sustained release** and a more consistent plasma concentration of the drug compared to oral administration.
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