Central Nervous System Pharmacology Practice Questions

Q: Which one of the following drugs is used in Alzheimer's disease?

Tacrine. **Explanation:** **Correct Option: A (Tacrine)** Alzheimer’s disease is characterized by a cholinergic deficiency in the brain. **Tacrine** is a centrally acting, reversible **acetylcholinesterase inhibitor (AChEI)**. By inhibiting the enzyme that breaks down acetylcholine, it increases the concentration of this neurotransmitter in the synaptic cleft, thereby improving cognitive function and memory in patients with mild-to-moderate Alzheimer's. While it was the first AChEI approved for this condition, its clinical use is now limited due to significant **hepatotoxicity** (frequent monitoring of ALT is required). **Incorrect Options:** * **B. Pemoline:** This is a CNS stimulant previously used for ADHD and narcolepsy. It is not used in Alzheimer's and has been largely withdrawn due to liver toxicity. * **C. Doxapram:** This is a **central respiratory stimulant** (analeptic). It acts on peripheral chemoreceptors to increase tidal volume and respiratory rate; it is typically used in acute respiratory failure or post-anesthesia respiratory depression. * **D. Methylphenidate:** A potent CNS stimulant (amphetamine-like) used primarily in the treatment of **ADHD** and **Narcolepsy**. It works by increasing dopamine and norepinephrine levels. **NEET-PG High-Yield Pearls:** * **First-line AChEIs for Alzheimer's:** Donepezil, Rivastigmine, and Galantamine (preferred over Tacrine due to better safety profiles). * **NMDA Receptor Antagonist:** **Memantine** is used for moderate-to-severe Alzheimer's, often as an adjunct to AChEIs. * **Rivastigmine** is unique as it is available as a **transdermal patch**, which improves compliance and reduces GI side effects. * **Galantamine** also acts as a nicotinic receptor modulator.

Q: Which drug can be used in the management of Sydenham’s chorea?

Haloperidol. **Explanation:** **Sydenham’s chorea** is a major manifestation of Acute Rheumatic Fever, characterized by involuntary, purposeless movements caused by autoimmune-mediated inflammation of the basal ganglia. The pathophysiology involves **dopaminergic overactivity** in the nigrostriatal pathway. **Why Haloperidol is correct:** Haloperidol is a potent **D2 receptor antagonist** (typical antipsychotic). By blocking dopamine receptors in the striatum, it effectively suppresses choreiform movements. It is considered one of the first-line pharmacological treatments for severe Sydenham’s chorea when symptoms interfere with daily activities or safety. **Analysis of Incorrect Options:** * **Valproate sodium & Carbamazepine:** While Valproate is sometimes used as a second-line alternative (due to its GABAergic effects) if dopamine antagonists are contraindicated, **Haloperidol** remains the classic, more frequently tested answer for chorea management. Carbamazepine is primarily an antiepileptic and has no established role in treating chorea. * **Phenytoin:** This is an antiepileptic drug that can actually **induce or worsen** chorea as a side effect; therefore, it is contraindicated in this clinical scenario. **Clinical Pearls for NEET-PG:** * **First-line management:** Most cases of Sydenham’s chorea are self-limiting and require only bed rest and penicillin prophylaxis. * **Drug of choice for movement control:** Haloperidol or Pimozide (D2 blockers). * **Alternative:** Sodium Valproate is preferred by some clinicians to avoid the risk of Extrapyramidal Side Effects (EPS) associated with Haloperidol. * **Steroids:** May be used in refractory cases to hasten recovery due to the autoimmune nature of the disease.

Q: Which of the following is NOT a mechanism of action of Levetiracetam?

Inhibits postsynaptic calcium channels. Explanation: Levetiracetam is a unique broad-spectrum antiepileptic drug (AED) with a mechanism of action distinct from traditional sodium or calcium channel blockers. Why Option C is correct: Levetiracetam does not inhibit postsynaptic calcium channels. Its primary action is presynaptic. While it may inhibit N-type calcium channels and reduce intracellular calcium release from the sarcoplasmic reticulum, its hallmark mechanism is binding to the Synaptic Vesicle Protein 2A (SV2A). This binding modulates the release of neurotransmitters (like glutamate and GABA) by regulating vesicle exocytosis. Analysis of other options: * Option A (Used in myoclonic epilepsy): This is a correct clinical use. Levetiracetam is a first-line agent for myoclonic seizures (including Juvenile Myoclonic Epilepsy) and is also used for focal and generalized tonic-clonic seizures. * Option B (Acts on GABA receptors): While not its primary mechanism, Levetiracetam has been shown to reverse the inhibition of GABA and glycine-gated currents by negative modulators (like zinc and ̢-carbolines), indirectly facilitating GABAergic transmission. * Option D (Binds to SV2A): This is the most characteristic mechanism of Levetiracetam. SV2A binding correlates directly with its anticonvulsant potency. High-Yield NEET-PG Pearls: * Pharmacokinetics: It has near 100% bioavailability, minimal protein binding, and is excreted unchanged in urine (requires dose adjustment in renal failure). * Drug Interactions: It has no significant CYP450 interactions, making it ideal for patients on multiple medications. * Side Effects: The most specific side effect is behavioral changes (irritability, aggression, or "Levy-rage") and somnolence. * Brivaracetam: A newer analog with higher affinity for SV2A.

Q: The clinical indications for tricyclic antidepressants include all of the following except?

Uncontrolled seizures. **Explanation:** The correct answer is **D. Uncontrolled seizures**. **1. Why Uncontrolled Seizures is the correct answer:** Tricyclic Antidepressants (TCAs), such as Amitriptyline and Imipramine, are known to **lower the seizure threshold**. This means they make the brain more susceptible to firing abnormal electrical discharges. Consequently, TCAs are generally **contraindicated** in patients with epilepsy or a history of seizures, as they can precipitate or worsen seizure activity. In cases of TCA overdose, seizures are a common and life-threatening complication. **2. Analysis of Incorrect Options:** * **A. Enuresis in elderly subjects:** While more commonly used for nocturnal enuresis in children (due to their anticholinergic effect which increases bladder capacity), TCAs like Imipramine have historically been used for urinary incontinence in the elderly. * **B. Neuropathic Pain:** TCAs are a first-line treatment for neuropathic pain (e.g., diabetic neuropathy, post-herpetic neuralgia). They work by enhancing descending inhibitory pathways through the inhibition of norepinephrine and serotonin reuptake. * **C. Panic Disorder:** TCAs (specifically Imipramine and Clomipramine) are effective in treating panic disorder and other anxiety disorders, although SSRIs are now preferred due to a better side-effect profile. **Clinical Pearls for NEET-PG:** * **The "3 Cs" of TCA Toxicity:** Coma, Convulsions, and Cardiotoxicity (arrhythmias due to sodium channel blockade). * **Antidote for Cardiotoxicity:** Sodium bicarbonate (NaHCO₃) is used to manage QRS widening and arrhythmias in TCA overdose. * **Drug of Choice for OCD:** Clomipramine (a TCA), though SSRIs are first-line. * **Nocturnal Enuresis:** Imipramine is the TCA used, but **Desmopressin** is currently the drug of choice.

Q: Regarding lamotrigine, which of the following statements is true?

It is a broad spectrum antiepileptic drug.. **Explanation:** **Lamotrigine** is a versatile antiepileptic drug (AED) primarily known for its **broad-spectrum activity**. 1. **Why Option C is Correct:** Lamotrigine is effective against a wide variety of seizure types, including focal (partial) seizures and generalized seizures (tonic-clonic, absence, and myoclonic). Its primary mechanism involves **blocking voltage-gated sodium (Na+) channels** in their inactivated state, which inhibits the release of excitatory neurotransmitters like **glutamate**. 2. **Why Other Options are Incorrect:** * **Option A:** Lamotrigine has no significant dopaminergic activity and is not used to treat Parkinsonism. * **Option B:** While it reduces glutamate release, its primary molecular target is the **sodium channel**, not the NMDA receptor (unlike drugs like Memantine or Ketamine). * **Option C vs D:** Unlike older narrow-spectrum drugs (e.g., Phenytoin or Carbamazepine), which can exacerbate absence seizures, Lamotrigine is effective in treating **absence seizures**. **High-Yield Clinical Pearls for NEET-PG:** * **Stevens-Johnson Syndrome (SJS):** The most dreaded side effect of Lamotrigine is a severe skin rash (SJS/TEN). To minimize this risk, the drug must be started at a low dose and **titrated very slowly**. * **Bipolar Disorder:** Beyond epilepsy, it is a first-line agent for the **maintenance treatment of Bipolar Depression**. * **Pregnancy:** It is considered one of the **safer AEDs during pregnancy** (lower teratogenic risk compared to Valproate), though clearance increases significantly during gestation. * **Drug Interaction:** Valproate inhibits Lamotrigine metabolism, doubling its half-life and significantly increasing the risk of life-threatening rashes.

Q: What is the drug of choice for idiopathic intracranial hypertension?

Acetazolamide. **Explanation:** **Idiopathic Intracranial Hypertension (IIH)**, also known as Pseudotumor Cerebri, is characterized by increased intracranial pressure (ICP) without an identifiable cause (like a tumor or obstruction). **Why Acetazolamide is the Drug of Choice:** Acetazolamide is a **Carbonic Anhydrase Inhibitor**. In the CNS, carbonic anhydrase is essential for the production of Cerebrospinal Fluid (CSF) by the choroid plexus. By inhibiting this enzyme, Acetazolamide significantly reduces the rate of CSF secretion, thereby lowering intracranial pressure. It is the first-line medical therapy, often combined with weight loss [1]. **Analysis of Incorrect Options:** * **B. Glycerol & C. Mannitol:** These are **osmotic diuretics**. While they are highly effective for the *acute* management of cerebral edema or life-threatening elevations in ICP (e.g., head injury), they are not suitable for the long-term management of IIH due to the risk of rebound ICP and electrolyte imbalances. * **D. Dexamethasone:** While glucocorticoids reduce ICP in cases of vasogenic edema (associated with brain tumors or abscesses), they are **not recommended** for IIH. In fact, steroid withdrawal can sometimes trigger or worsen IIH. **Clinical Pearls for NEET-PG:** * **Classic Presentation:** Obese female of childbearing age presenting with headache, papilledema, and "whooshing" tinnitus (pulsatile). * **Side Effects of Acetazolamide:** Paresthesia (most common), metabolic acidosis, and hypokalemia [1]. * **Alternative:** If Acetazolamide is not tolerated, **Topiramate** is an alternative as it also has weak carbonic anhydrase inhibitory activity and aids in weight loss. * **Surgical Management:** If medical therapy fails and vision is threatened, Optic Nerve Sheath Fenestration or CSF shunting is performed.

Q: Which of the following is NOT a first-line choice drug for epilepsy in pregnancy?

Sodium valproate. ### Explanation **Sodium Valproate** is the correct answer because it is strictly contraindicated as a first-line agent in pregnancy due to its high **teratogenic potential**. It is associated with a significantly higher risk of major congenital malformations (MCMs) compared to other anti-epileptic drugs (AEDs). #### Why Sodium Valproate is avoided: * **Neural Tube Defects (NTDs):** It carries a 1–2% risk of spina bifida (due to interference with folate metabolism). * **Fetal Valproate Syndrome:** Characterized by craniofacial anomalies, cardiovascular defects, and limb abnormalities. * **Neurodevelopmental Delay:** Prenatal exposure is linked to lower IQ scores and increased risk of autism spectrum disorders in children. #### Why other options are incorrect: * **Lamotrigine (B) and Levetiracetam (C):** These are currently considered the **safest and preferred first-line choices** in pregnancy. They have the lowest reported rates of major malformations. * **Carbamazepine (A):** While it carries a slightly higher risk than Lamotrigine (specifically for cleft lip/palate), it is still significantly safer than Valproate and is considered a viable first-line option if the patient is already well-controlled on it. #### High-Yield Clinical Pearls for NEET-PG: 1. **Drug of Choice (DOC):** If a woman on Valproate plans pregnancy, she should be switched to **Levetiracetam** or **Lamotrigine** before conception. 2. **Folic Acid:** All pregnant women on AEDs should take high-dose folic acid (5 mg/day) to reduce NTD risks. 3. **Enzyme Inducers:** Carbamazepine and Phenytoin induce hepatic enzymes, which can lead to Vitamin K deficiency in the newborn; hence, Vitamin K prophylaxis is essential at birth. 4. **Monotherapy:** The gold standard for managing epilepsy in pregnancy is to use the **lowest effective dose** of a **single drug** (monotherapy).

Q: Which of the following conditions respond well with clonidine?

All of the above. **Explanation:** Clonidine is a centrally acting **$\alpha_2$-adrenergic agonist**. By stimulating presynaptic $\alpha_2$ receptors in the brainstem (specifically the vasomotor center and locus coeruleus), it reduces sympathetic outflow, leading to a decrease in peripheral resistance and heart rate. Beyond its use as an antihypertensive, its ability to modulate catecholamine release makes it effective in several neuropsychiatric conditions. * **Opiate Withdrawal:** Clonidine suppresses the sympathetic overactivity (tachycardia, hypertension, sweating, and anxiety) caused by the "noradrenergic storm" that occurs during opioid withdrawal. It is a standard non-opioid treatment for managing these autonomic symptoms. * **Attention-Deficit/Hyperactivity Disorder (ADHD):** It is used as a second-line or adjunctive treatment, particularly in children who do not tolerate stimulants or have comorbid tics. It works by modulating prefrontal cortex activity. * **Tourette’s Disorder:** Clonidine (and Guanfacine) are often preferred initial treatments for tics because they have a better side-effect profile compared to antipsychotics (haloperidol/pimozide). **Clinical Pearls for NEET-PG:** 1. **Rebound Hypertension:** Sudden withdrawal of clonidine can cause a hypertensive crisis due to a massive surge in catecholamines. 2. **Guanfacine:** A more selective $\alpha_{2A}$ agonist than clonidine, often preferred in ADHD due to less sedation and longer duration of action. 3. **Other Uses:** Clonidine is also used in the prophylaxis of **migraine**, treatment of **menopausal hot flashes**, and as a diagnostic test for **pheochromocytoma** (Clonidine Suppression Test). 4. **Side Effects:** Most common are sedation, xerostomia (dry mouth), and bradycardia.

Question 1

Which one of the following drugs is used in Alzheimer's disease?

Accepted Answer

Tacrine

Answer

Pemoline

Answer

Doxapram

Answer

Methylphenidate

Question 2

Which drug can be used in the management of Sydenham’s chorea?

Accepted Answer

Haloperidol

Answer

Valproate sodium

Answer

Carbamazepine

Answer

Phenytoin

Question 3

Which of the following is NOT a mechanism of action of Levetiracetam?

Accepted Answer

Inhibits postsynaptic calcium channels

Answer

Used in myoclonic epilepsy

Answer

Acts on GABA receptors

Answer

Binds to SV2A and regulates neurotransmitter exocytosis

Question 4

The clinical indications for tricyclic antidepressants include all of the following except?

Accepted Answer

Uncontrolled seizures

Answer

Enuresis in elderly subjects

Answer

Neuropathic pain

Answer

Panic disorder

Question 5

Regarding lamotrigine, which of the following statements is true?

Accepted Answer

It is a broad spectrum antiepileptic drug.

Answer

It is a dopaminergic agonist used in Parkinsonism.

Answer

It acts by blocking NMDA type of glutamate receptors.

Answer

It suppresses tonic-clonic seizures but worsens absence seizures.

Question 6

What is the drug of choice for idiopathic intracranial hypertension?

Accepted Answer

Acetazolamide

Answer

Glycerol

Answer

Mannitol

Answer

Dexamethasone

Question 7

Which of the following is NOT a first-line choice drug for epilepsy in pregnancy?

Accepted Answer

Sodium valproate

Answer

Carbamazepine

Answer

Lamotrigine

Answer

Levetiracetam

Question 8

What is the most serious side effect of valproate?

Accepted Answer

Fulminant hepatitis

Answer

Spina bifida

Answer

Weight gain

Answer

Thrombocytopenia

Question 9

Which of the following conditions respond well with clonidine?

Accepted Answer

All of the above

Answer

Opiate withdrawal

Answer

Attention-deficit/hyperactivity disorder

Answer

Tourette's disorder

Question 10

In a patient receiving a ketogenic diet for epilepsy, which one of the following antiepileptic agents should be avoided?

Accepted Answer

Sodium valproate

Answer

Phenytoin

Answer

Carbamazepine

Answer

Lamotrigine

Central Nervous System Pharmacology — MCQs

Central Nervous System Pharmacology — MCQs

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