Central Nervous System Pharmacology Practice Questions

Q: Which of the following is a non-cholinergic agent?

Memantine. ***Memantine*** - Memantine is an **NMDA receptor antagonist** and works by blocking the effects of excessive **glutamate**, a neurotransmitter that can contribute to neuronal damage in Alzheimer's disease. - Unlike the other options, it does not directly interfere with the **acetylcholine** system but rather modulates glutamatergic neurotransmission. *Galantamine* - Galantamine is an **acetylcholinesterase inhibitor** and an allosteric modulator of nicotinic acetylcholine receptors. - It increases the availability of **acetylcholine** in the synaptic cleft, making it a cholinergic agent. *Donepezil* - Donepezil is a **reversible acetylcholinesterase inhibitor** used in the treatment of Alzheimer's disease. - Its mechanism of action involves increasing the concentration of **acetylcholine** in the brain, thus it is a cholinergic agent. *Tacrine* - Tacrine was one of the first **acetylcholinesterase inhibitors** approved for Alzheimer's disease. - It works by preventing the breakdown of **acetylcholine**, thereby increasing its levels in the brain and is considered a cholinergic agent.

Q: Which of the following drugs is least preferred for the treatment of multiple sclerosis?

Mycophenolate. ***Mycophenolate*** - **Mycophenolate mofetil** is an immunosuppressant typically used to prevent **organ transplant rejection** and in autoimmune diseases like **lupus nephritis**. - While it has immunosuppressive properties, it is **not approved** or considered a first-line or even second-line treatment for **multiple sclerosis (MS)** due to a lack of robust evidence of efficacy and a less favorable risk-benefit profile compared to other established MS therapies. *Interferon beta-1a* - **Interferon beta-1a** is a **disease-modifying therapy (DMT)** widely used for **relapsing-remitting multiple sclerosis (RRMS)**, reducing relapse rates and slowing disease progression. - It works by modulating the **immune response** to decrease inflammation and demyelination in the central nervous system. *Interferon beta-1b* - Similar to interferon beta-1a, **interferon beta-1b** is an established **DMT** for **RRMS** and some forms of **secondary progressive MS**. - It also functions through **immunomodulation**, helping to reduce the frequency and severity of relapses. *Glatiramer acetate* - **Glatiramer acetate** is an **immunomodulator** approved for the treatment of **RRMS**, working by mimicking myelin basic protein and inducing T-cell tolerance. - It effectively **reduces relapse rates** and is considered a safe and well-tolerated option for long-term use in MS patients.

Q: The drug of choice for absence attacks is

Ethosuximide. ***Ethosuximide*** - **Ethosuximide** is the most effective and preferred drug for treating **absence seizures** due to its selective mechanism of action. - It works by blocking **T-type calcium channels** in the thalamus, which are crucial for generating the characteristic 3-Hz spike-and-wave discharges of absence seizures. *Phenytoin* - **Phenytoin** is primarily used for **tonic-clonic seizures** and **focal seizures**, but it is generally ineffective for absence seizures and can even worsen them. - Its mechanism of action involves stabilizing neuronal membranes by **blocking voltage-gated sodium channels**, which is not the primary pathophysiology of absence seizures. *Primidone* - **Primidone** is an anticonvulsant that is metabolized to **phenobarbital** and **phenylethylmalonamide (PEMA)**. It is effective for **generalized tonic-clonic** and **focal seizures**. - It is not considered a first-line treatment for **absence seizures** and may not be effective. *Phenobarbitone* - **Phenobarbitone** (phenobarbital) is a barbiturate effective against **generalized tonic-clonic** and **focal seizures** but is not a drug of choice for absence seizures. - While it has broad-spectrum anticonvulsant activity by enhancing **GABAergic inhibition**, it is less effective and has more prominent sedative side effects compared to ethosuximide for absence epilepsy.

Q: Diplopia and ataxia are the adverse effects of which of the following drugs?

Phenytoin and carbamazepine. ***Phenytoin and carbamazepine*** - Both **phenytoin** and **carbamazepine** are well-known to cause **diplopia** (double vision) and **ataxia** (impaired coordination) as dose-related adverse effects, especially at higher therapeutic levels. - These neurological side effects occur due to their impact on the **central nervous system**, affecting motor control and ocular movements. *Gabapentin and carbamazepine* - While **carbamazepine** can cause diplopia and ataxia, **gabapentin** primarily causes dizziness, drowsiness, and fatigue, but less commonly diplopia or significant ataxia at therapeutic doses. - Gabapentin's mechanism of action differs from carbamazepine, leading to a distinct adverse effect profile. *Gabapentin with phenytoin* - **Phenytoin** is associated with diplopia and ataxia, but **gabapentin** is less likely to cause these specific effects compared to phenytoin. - The combination would not be the primary answer for both drugs specifically causing prominent diplopia and ataxia. *Valproate and topiramate* - **Valproate** can cause tremor and sedation but is less commonly associated with prominent diplopia and ataxia. - **Topiramate** frequently causes cognitive slowing, word-finding difficulties, and paresthesias, but diplopia and ataxia are not its most characteristic adverse effects.

Q: Which one of the following drugs has a narrow therapeutic range?

Phenytoin. ***Phenytoin*** - **Phenytoin** has a **narrow therapeutic index**, meaning there is a small difference between the therapeutic and toxic doses. - This necessitates **therapeutic drug monitoring** to ensure effective treatment while avoiding adverse effects like nystagmus, ataxia, or gingival hyperplasia. *Propranolol* - **Propranolol** is a **beta-blocker** used for hypertension, angina, and arrhythmias, generally considered to have a wide therapeutic range. - While dose adjustments are common, routine therapeutic drug monitoring is typically **not required** due to its relatively safe profile at higher doses compared to drugs like phenytoin. *Piroxicam* - **Piroxicam** is a **nonsteroidal anti-inflammatory drug (NSAID)** with a relatively wide therapeutic window. - Its primary concerns are gastrointestinal and renal side effects rather than toxicity from a narrow therapeutic range. *Prazosin* - **Prazosin** is an **alpha-1 adrenergic blocker** used for hypertension and benign prostatic hyperplasia, and it generally has a wide therapeutic range. - The main concern with prazosin is **first-dose phenomenon** (orthostatic hypotension), which is an initial effect rather than toxicity from a narrow therapeutic window.

Q: Which of the following is FALSE about ropivacaine?

Contains only R enantiomer. ***Contains only R enantiomer*** - Ropivacaine is a **pure S-enantiomer** (S-(-)-enantiomer) preparation, NOT the R-enantiomer. - This single enantiomer formulation contributes to its **reduced cardiotoxicity** and improved safety profile compared to racemic bupivacaine. - The statement "contains only R enantiomer" is **FALSE** - this is the correct answer. *Less cardiotoxic than bupivacaine* - Ropivacaine has **lower lipid solubility** and faster dissociation from cardiac sodium channels compared to bupivacaine. - This results in **significantly reduced cardiotoxicity**, making it safer for large-volume regional blocks. - This statement is **TRUE**. *More cardiotoxic than lignocaine* - Ropivacaine is indeed **more cardiotoxic than lidocaine** due to its greater potency and longer duration of action. - Amide local anesthetics with higher potency (bupivacaine > ropivacaine > lidocaine) carry greater cardiac risk. - This statement is **TRUE**. *Onset of action is faster than bupivacaine* - Ropivacaine and bupivacaine have **similar onset times** (10-15 minutes for epidural/nerve blocks). - Both have similar pKa values (ropivacaine 8.1, bupivacaine 8.1), resulting in comparable onset characteristics. - While ropivacaine may have marginally faster onset in some contexts, clinically they are considered equivalent. - This statement is generally **FALSE or equivocal**, making it potentially the second-best answer, but the R-enantiomer statement is definitively false.

Q: Which ergot-derived dopamine receptor agonist is known to cause cardiac valvular fibrosis?

Pergolide & cabergoline. ***Pergolide & cabergoline*** - Both **Pergolide** and **Cabergoline** are **ergot-derived dopamine agonists** [1], [2], [3] that have been associated with **cardiac valvular fibrosis** [1], [2]. - This adverse effect is mediated by their agonistic activity on **5-HT2B serotonin receptors** located on heart valve fibroblasts [2]. *Levodopa* - **Levodopa** is a precursor to dopamine and is used to treat Parkinson's disease, but it is not an ergot derivative [1]. - It does not directly cause cardiac valvular fibrosis; its main side effects are related to motor complications and gastrointestinal issues. *Ropinrole* - **Ropinrole** is a **non-ergot dopamine agonist** used for Parkinson's disease and restless legs syndrome [1]. - Unlike ergot-derived agonists, it has a lower affinity for 5-HT2B receptors and is not significantly associated with cardiac valvular fibrosis. *Pramipexole* - **Pramipexole** is another **non-ergot dopamine agonist** with a similar safety profile to ropinirole regarding cardiac health [1]. - It does not cause cardiac valvular fibrosis and is generally preferred over ergot derivatives due to their cardiovascular side effects.

Q: What is the classification of Sumatriptan?

5HT 1B/1D agonist. ***5HT 1B/1D agonist*** - Sumatriptan is a **selective serotonin receptor agonist**, specifically targeting the **5-HT1B** and **5-HT1D** receptor subtypes. - This is the **precise pharmacological classification** of triptans used in acute migraine treatment. - Agonism at **5-HT1B receptors** causes **vasoconstriction** of dilated cranial blood vessels. - Agonism at **5-HT1D receptors** inhibits the release of **pro-inflammatory neuropeptides** (CGRP, substance P) from trigeminal nerve endings. - This specific classification distinguishes sumatriptan from non-selective serotonin agonists. *5HT 1 agonist* - While technically not incorrect, this classification is **too broad and imprecise** for pharmacological purposes. - A general "5-HT1 agonist" could theoretically include activity at 5-HT1A, 1B, 1D, 1E, and 1F receptors. - Sumatriptan has **minimal affinity** for 5-HT1A receptors and its therapeutic effect is specifically due to 5-HT1B/1D activity. - In medical literature and standard pharmacology texts, triptans are classified as **5-HT1B/1D agonists**, not general 5-HT1 agonists. *5HT 1D antagonist* - An **antagonist** blocks receptor activity rather than activating it. - This would **worsen** migraine symptoms by preventing the therapeutic effects of endogenous serotonin. - There are no established antimigraine drugs that act as 5-HT1D antagonists. *5HT 1A antagonist* - 5-HT1A receptors are primarily involved in **mood regulation, anxiety, and sleep**, not acute migraine pathophysiology. - Sumatriptan has minimal activity at 5-HT1A receptors. - Antagonism at this receptor would not provide antimigraine effects and is unrelated to sumatriptan's mechanism.

Q: Most cardiotoxic local anesthetic is:

Bupivacaine. ***Bupivacaine*** - **Bupivacaine** is a **highly potent** local anesthetic known for its cardiotoxic effects due to its **lipophilicity** and strong binding to cardiac sodium channels. - Its **slow dissociation** from cardiac sodium channels at toxic plasma concentrations contributes to prolonged arrhythmias and myocardial depression. *Lidocaine* - **Lidocaine** has a **faster onset** and shorter duration of action compared to bupivacaine, making it less cardiotoxic. - While it can cause cardiac effects at high doses, it generally has a **safer cardiac profile** than bupivacaine and is often used as an antiarrhythmic. *Procaine* - **Procaine** is an **ester-type** local anesthetic, which means it is rapidly metabolized by plasma cholinesterases. - This rapid breakdown gives it a **short duration of action** and a **low potential for systemic toxicity**, including cardiotoxicity. *Ropivacaine* - **Ropivacaine** is a **less lipophilic** analog of bupivacaine, designed to have a reduced cardiotoxicity profile. - While it still has potential for cardiotoxicity at very high doses, it demonstrates a **higher therapeutic index** for cardiac rhythm compared to bupivacaine.

Q: Which one of the following drugs does not interfere with folic acid metabolism?

Gabapentin. ***Gabapentin*** - **Gabapentin** is an anticonvulsant that primarily exerts its effects by modulating activity at voltage-gated calcium channels; it does **not interfere with folic acid metabolism**. - Its mechanism of action is distinct from other antiepileptic drugs that are known to cause folate deficiency. *Phenobarbitone* - **Phenobarbitone** is an antiepileptic drug that belongs to the barbiturate class and is known to be an **inducer of hepatic microsomal enzymes**. - This enzyme induction can **increase the metabolism of folic acid**, leading to its depletion and potentially megaloblastic anemia. *Primidone* - **Primidone** is an antiepileptic drug that is metabolized to **phenobarbitone** and phenylethylmalonamide (PEMA). - Like phenobarbitone, it is an **hepatic enzyme inducer** and can therefore **interfere with folic acid metabolism**. *Phenytoin* - **Phenytoin** is a well-known antiepileptic drug that often causes **folate deficiency**. - It interferes with folate metabolism by **inhibiting intestinal folate absorption** and by increasing its breakdown through enzyme induction.

Question 1

Which of the following is a non-cholinergic agent?

Accepted Answer

Memantine

Answer

Galantamine

Answer

Donepezil

Answer

Tacrine

Question 2

Which of the following drugs is least preferred for the treatment of multiple sclerosis?

Accepted Answer

Mycophenolate

Answer

Interferon beta-1b

Answer

Interferon beta-1a

Answer

Glatiramer acetate

Question 3

The drug of choice for absence attacks is

Accepted Answer

Ethosuximide

Answer

Phenytoin

Answer

Primidone

Answer

Phenobarbitone

Question 4

Diplopia and ataxia are the adverse effects of which of the following drugs?

Accepted Answer

Phenytoin and carbamazepine

Answer

Gabapentin and carbamazepine

Answer

Gabapentin with phenytoin

Answer

Valproate and topiramate

Question 5

Which one of the following drugs has a narrow therapeutic range?

Accepted Answer

Phenytoin

Answer

Propranolol

Answer

Piroxicam

Answer

Prazosin

Question 6

Which of the following is FALSE about ropivacaine?

Accepted Answer

Contains only R enantiomer

Answer

More cardiotoxic than lignocaine

Answer

Less cardiotoxic than bupivacaine

Answer

Onset of action is faster than bupivacaine

Question 7

Which ergot-derived dopamine receptor agonist is known to cause cardiac valvular fibrosis?

Accepted Answer

Pergolide & cabergoline

Answer

Levodopa

Answer

Ropinrole

Answer

Pramipexole

Question 8

What is the classification of Sumatriptan?

Accepted Answer

5HT 1B/1D agonist

Answer

5HT 1D antagonist

Answer

5HT 1A antagonist

Answer

5HT 1 agonist

Question 9

Most cardiotoxic local anesthetic is:

Accepted Answer

Bupivacaine

Answer

Procaine

Answer

Lidocaine

Answer

Ropivacaine

Question 10

Which one of the following drugs does not interfere with folic acid metabolism?

Accepted Answer

Gabapentin

Answer

Phenobarbitone

Answer

Primidone

Answer

Phenytoin

Central Nervous System Pharmacology — MCQs

Central Nervous System Pharmacology — MCQs

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