Central Nervous System Pharmacology Practice Questions

Q: Which of the following nerve fibre types is least susceptible to LA blockade?

A alpha. **A alpha** - **A alpha fibers** are the **largest** and most heavily myelinated nerve fibers, responsible for **motor function** and **proprioception**. - Due to their large diameter and thick myelination, they have the **highest conduction velocity** and are the **least susceptible to local anesthetic blockade**, requiring higher concentrations or longer exposure times. *B fibers* - **B fibers** are **preganglionic autonomic fibers** that are myelinated but of relatively small diameter. - They are generally **highly sensitive to local anesthetics**, often being blocked even before A-delta and C fibers, due to their specific physiologic properties like repetitive firing and length of node of Ranvier. *C fibers* - **C fibers** are **unmyelinated** and have the **smallest diameter**, transmitting **pain, temperature, and autonomic information**. - Despite being unmyelinated, their small diameter makes them **highly sensitive to local anesthetics**, as the drug can easily penetrate to block sodium channels. *A beta* - **A beta fibers** are large, myelinated fibers involved in transmitting **touch and pressure sensations**. - While myelinated, they are **smaller than A-alpha fibers** and thus more susceptible to local anesthetic blockade than A-alpha, but less so than C or B fibers.

Q: Which anti-epileptic drug is most likely to cause aplastic anemia?

Carbamazepine. ***Carbamazepine*** - **Carbamazepine** is an anti-epileptic drug that can cause **aplastic anemia** as a rare but serious adverse effect. It is also known to cause other hematological side effects like leukopenia and thrombocytopenia. - Regular monitoring of **complete blood counts** is recommended, especially during the initial phases of treatment, due to this risk. *Phenytoin* - While **phenytoin** can cause various adverse effects, including **folate deficiency** leading to megaloblastic anemia, it is not typically associated with **aplastic anemia**. - Other common side effects include gingival hyperplasia, hirsutism, and Stevens-Johnson syndrome. *Levetiracetam* - **Levetiracetam** is generally well-tolerated and is rarely associated with severe hematological adverse events like **aplastic anemia**. - Its most common side effects are somnolence, asthenia, and behavioral changes. *Valproate* - **Valproate** can cause **thrombocytopenia** and, in rare instances, bone marrow suppression, but it is not a primary cause of **aplastic anemia**. - Its most concerning adverse effects include hepatotoxicity and pancreatitis.

Q: A 50-year-old with Parkinson's disease is on levodopa. Adding which drug helps manage 'wearing-off' effects?

Entacapone. ***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.

Q: Which sedative is most appropriate in a patient with hepatic impairment?

Lorazepam. ***Lorazepam*** - **Lorazepam** is primarily metabolized by **glucuronidation**, a phase II metabolic pathway that is relatively preserved in most forms of hepatic impairment - This makes it a safer choice in patients with **liver disease** compared to other benzodiazepines that rely heavily on oxidative metabolism - Preferred sedative in cirrhosis and acute liver failure *Midazolam* - **Midazolam** is primarily metabolized by the **cytochrome P450 3A4 (CYP3A4)** enzyme system in the liver - Hepatic impairment can significantly reduce **CYP3A4 activity**, leading to prolonged half-life, increased sedative effects, and accumulation of the drug - Should be avoided or dose-reduced in hepatic impairment *Zolpidem* - **Zolpidem** is extensively metabolized by **hepatic cytochrome P450 enzymes**, particularly CYP3A4 and CYP2C9 - In patients with **hepatic impairment**, its clearance is significantly reduced, necessitating dose reduction to avoid excessive sedation and adverse effects - Maximum dose should be limited to 5 mg in hepatic dysfunction *Diazepam* - **Diazepam** undergoes extensive **hepatic oxidative metabolism** via CYP2C19 and CYP3A4 to active metabolites such as **desmethyldiazepam**, which also have long half-lives - In patients with **liver disease**, this metabolism is impaired, leading to prolonged drug action, increased sedation, and accumulation of the parent drug and active metabolites - Active metabolites can accumulate for days to weeks in hepatic impairment

Q: Which of the following drugs is most associated with neuroleptic malignant syndrome?

Haloperidol. ***Haloperidol*** - **Haloperidol** is a potent **first-generation antipsychotic** that strongly blocks **D2 dopamine receptors**. - This strong dopamine antagonism, particularly in the **nigrostriatal pathway**, is a primary mechanism underlying the development of **Neuroleptic Malignant Syndrome (NMS)**. *Clozapine* - Although clozapine is an antipsychotic, it is associated with a **lower risk of NMS** compared to high-potency typical antipsychotics. - Its unique pharmacological profile, including **weak D2 receptor blockade** and antagonism of other receptors, contributes to its reduced NMS risk. *Quetiapine* - Quetiapine is an **atypical (second-generation) antipsychotic** known for its **low risk of extrapyramidal symptoms (EPS)** and thus NMS. - Its relatively **loose binding to D2 receptors** and rapid dissociation significantly lowers the likelihood of severe dopamine blockade. *Olanzapine* - Olanzapine is another **atypical antipsychotic** with a **lower incidence of NMS** compared to typical antipsychotics like haloperidol. - While it has D2 receptor antagonism, it is less potent and more balanced by other receptor effects, leading to a reduced risk of NMS.

Q: Cannabidiol is not used for

Rett syndrome. ***Rett syndrome*** - **Cannabidiol (CBD)** is not an approved or commonly used treatment for Rett syndrome, which is a **neurodevelopmental disorder** primarily affecting girls. - Treatment for Rett syndrome focuses on managing symptoms with supportive care, **physiotherapy**, occupational therapy, and medications for specific issues like seizures or gastrointestinal problems. *Dravet syndrome* - **Cannabidiol (Epidiolex)** is approved in many regions for the treatment of seizures associated with **Dravet syndrome**, a severe form of epilepsy. - It works by modulating the **endocannabinoid system**, which plays a role in seizure control. *Lennox-Gastaut syndrome* - **Cannabidiol (Epidiolex)** is also approved for the treatment of seizures associated with **Lennox-Gastaut syndrome**, another severe and intractable childhood epilepsy. - Its efficacy in reducing seizure frequency in LGS has been demonstrated in clinical trials. *Tuberous sclerosis complex* - While not as widely established as for Dravet or Lennox-Gastaut, **cannabidiol (Epidiolex)** has shown promise and is approved in some regions for treating seizures associated with **tuberous sclerosis complex (TSC)**. - TSC is a genetic disorder causing benign tumors in multiple organs, often leading to epilepsy.

Q: In which of the following conditions are cannabinoids not commonly used for treatment?

Rett syndrome. ***Rett syndrome*** - Cannabinoids are **NOT commonly used** as an established treatment for **Rett syndrome** - While some research is exploring their potential therapeutic role, they remain **investigational only** and lack FDA approval for this indication - Current management focuses on symptomatic treatment including physical therapy, anti-epileptics for seizures, and supportive care - Unlike the other conditions listed, there is **no established cannabinoid therapy** for Rett syndrome in clinical practice *Dravet syndrome* - **Cannabidiol (CBD/Epidiolex)** is **FDA-approved** and commonly used for treatment of seizures associated with **Dravet syndrome** - Demonstrates significant efficacy in reducing seizure frequency in this severe infantile-onset epilepsy - Represents a major therapeutic advance for this treatment-resistant condition *Tuberous sclerosis* - **Cannabidiol (CBD/Epidiolex)** received **FDA approval in 2018** for treatment of seizures associated with **tuberous sclerosis complex (TSC)** - Commonly used as an adjunctive therapy alongside other treatments like vigabatrin or mTOR inhibitors (everolimus) - Clinical trials demonstrated significant reduction in seizure frequency in TSC patients *Lennox-Gastaut Syndrome* - **Cannabidiol (CBD/Epidiolex)** is **FDA-approved** for seizures associated with **Lennox-Gastaut Syndrome (LGS)** - Commonly used in this severe epileptic encephalopathy characterized by multiple seizure types and developmental delay - Effective in reducing seizure burden in patients refractory to traditional anti-epileptic drugs

Q: A 35-year-old with migraines needs prophylaxis. Which is suitable?

Verapamil. ***Verapamil*** - **Verapamil**, a calcium channel blocker, is often used off-label for **migraine prophylaxis**, particularly in cases where other first-line agents are contraindicated or ineffective. - While not a first-line treatment, it can reduce the frequency and severity of migraine attacks by modulating **vasoconstriction** and **vasodilation**. *Acetaminophen* - **Acetaminophen** is an analgesic used for **acute pain relief**, but it does not have properties that prevent migraine attacks from occurring. - It is unsuitable for long-term **prophylactic management** of migraines. *Sumatriptan* - **Sumatriptan** is a **triptan** medication used for **acute migraine treatment**, meaning it is taken to stop a migraine attack once it has started. - It is not indicated for **migraine prophylaxis** and should not be used regularly to prevent migraines. *Tramadol* - **Tramadol** is an **opioid analgesic** used for moderate to severe pain, and it carries risks of dependence and side effects. - It is not recommended for **migraine prophylaxis** due to its addictive potential and lack of evidence for preventing migraine attacks.

Q: 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?

Ropinirole. ***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.

Q: Why are patients with Parkinson’s disease often treated with levodopa?

To increase dopamine levels in the brain. ***To increase dopamine levels in the brain*** - **Levodopa** is a precursor to **dopamine** and is used to replenish dopamine levels in the brain, as Parkinson's disease is characterized by the degeneration of dopaminergic neurons in the **substantia nigra**. - Since dopamine itself cannot cross the **blood-brain barrier**, levodopa is administered and then converted into dopamine within the brain, thereby alleviating motor symptoms. *To inhibit serotonin production* - **Serotonin** is a neurotransmitter involved in mood, sleep, and appetite, but its production is not the primary target in Parkinson's disease treatment. - While there can be interactions and indirect effects, levodopa's main mechanism does not involve inhibiting serotonin. *To block norepinephrine activity* - **Norepinephrine** is a neurotransmitter involved in alertness and fight-or-flight responses, and while it can be affected in Parkinson's disease, blocking its activity is not the primary goal of levodopa treatment. - Medications that block norepinephrine are typically used for conditions like anxiety or hypertension, not to treat the core symptoms of Parkinson's. *To decrease acetylcholine levels in the brain* - Decreasing **acetylcholine** levels is a strategy used for some Parkinson's symptoms, particularly tremors, using **anticholinergic drugs**. - However, this is a separate pharmacological approach and not the mechanism of action for levodopa, which focuses on increasing dopamine.

Question 1

Which of the following nerve fibre types is least susceptible to LA blockade?

Accepted Answer

A alpha

Answer

B fibers

Answer

A beta

Answer

C fibers

Question 2

Which anti-epileptic drug is most likely to cause aplastic anemia?

Accepted Answer

Carbamazepine

Answer

Phenytoin

Answer

Levetiracetam

Answer

Valproate

Question 3

A 50-year-old with Parkinson's disease is on levodopa. Adding which drug helps manage 'wearing-off' effects?

Accepted Answer

Entacapone

Answer

Amantadine

Answer

Selegiline

Answer

Bromocriptine

Question 4

Which sedative is most appropriate in a patient with hepatic impairment?

Accepted Answer

Lorazepam

Answer

Midazolam

Answer

Zolpidem

Answer

Diazepam

Question 5

Which of the following drugs is most associated with neuroleptic malignant syndrome?

Accepted Answer

Haloperidol

Answer

Clozapine

Answer

Quetiapine

Answer

Olanzapine

Question 6

Cannabidiol is not used for

Accepted Answer

Rett syndrome

Answer

Lennox-Gastaut syndrome

Answer

Dravet syndrome

Answer

Tuberous sclerosis complex

Question 7

In which of the following conditions are cannabinoids not commonly used for treatment?

Accepted Answer

Rett syndrome

Answer

Tuberous sclerosis

Answer

Lennox-Gastaut Syndrome

Answer

Dravet syndrome

Question 8

A 35-year-old with migraines needs prophylaxis. Which is suitable?

Accepted Answer

Verapamil

Answer

Acetaminophen

Answer

Sumatriptan

Answer

Tramadol

Question 9

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?

Accepted Answer

Ropinirole

Answer

Phenytoin

Answer

Aspirin

Answer

Gabapentin

Question 10

Why are patients with Parkinson’s disease often treated with levodopa?

Accepted Answer

To increase dopamine levels in the brain

Answer

To decrease acetylcholine levels in the brain

Answer

To inhibit serotonin production

Answer

To block norepinephrine activity

Central Nervous System Pharmacology — MCQs

Central Nervous System Pharmacology — MCQs

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