Central Nervous System Pharmacology Practice Questions

Q: The dose of which of the following local anesthetics does NOT need to be decreased in patients with deranged liver function?

Procaine. **Explanation:** The metabolism of local anesthetics (LAs) depends entirely on their chemical structure, specifically the linkage between the aromatic ring and the hydrocarbon chain. **1. Why Procaine is Correct:** Local anesthetics are classified into two groups: **Amides** and **Esters**. * **Esters** (e.g., Procaine, Chloroprocaine, Tetracaine) are metabolized by **pseudocholinesterase (plasma cholinesterase)** enzymes in the blood. * Since their metabolism occurs primarily in the plasma and not the liver, their clearance is largely independent of hepatic function. Therefore, the dose of Procaine does not need to be adjusted in patients with liver disease. **2. Why the Other Options are Incorrect:** * **Lignocaine and Bupivacaine (Amides):** Amide LAs (identified by having two "i"s in their name) are metabolized primarily by **hepatic microsomal enzymes** (Cytochrome P450). In patients with deranged liver function or reduced hepatic blood flow (e.g., CHF, cirrhosis), the half-life of these drugs is significantly prolonged, increasing the risk of Systemic Toxicity (LAST). Thus, doses must be decreased. * **Cocaine:** Although an ester, cocaine is unique because it undergoes significant metabolism by **hepatic carboxylesterase** in addition to plasma cholinesterase. Therefore, its clearance can still be affected by liver dysfunction. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic:** Am**i**des have two "i"s (L**i**doca**i**ne, Bup**i**vaca**i**ne, Pr**i**loca**i**ne, Rop**i**vaca**i**ne). Esters have one "i" (Proca**i**ne, Coca**i**ne, Benzoca**i**ne). * **Prilocaine** is associated with **Methemoglobinemia** (due to its metabolite o-toluidine). * **Bupivacaine** is the most **cardiotoxic** LA; Intralipid (20% lipid emulsion) is the specific antidote for toxicity. * **Chloroprocaine** has the shortest duration of action and fastest metabolism among esters.

Q: What is the drug of choice for generalized tonic-clonic status epilepticus?

Lorazepam. **Explanation:** **Status Epilepticus (SE)** is a medical emergency defined as a continuous seizure lasting more than 5 minutes or recurrent seizures without recovery of consciousness between episodes. **Why Lorazepam is the Correct Answer:** Benzodiazepines are the first-line treatment for terminating active seizures due to their rapid onset of action and high affinity for GABA-A receptors, which enhances inhibitory neurotransmission. **Lorazepam** is the preferred drug of choice (DOC) over Diazepam because it is less lipid-soluble; it remains in the vascular compartment longer, providing a more sustained anticonvulsant effect (6–12 hours) compared to the rapid redistribution of Diazepam. **Analysis of Incorrect Options:** * **A. Ethosuximide:** This is the DOC for **Absence seizures** only. It works by blocking T-type calcium channels and has no role in managing status epilepticus or tonic-clonic seizures. * **B. Sodium Valproate:** While a broad-spectrum anticonvulsant used for maintenance therapy in GTCS, it is considered a second-line agent in SE (used if benzodiazepines fail). * **C. Lamotrigine:** This is used for long-term prophylaxis of various seizures and bipolar disorder. It is not available in a rapid-acting intravenous formulation suitable for emergency seizure termination. **High-Yield Clinical Pearls for NEET-PG:** * **Sequence of Management in SE:** 1. **1st Line:** Lorazepam (IV) or Midazolam (IM/Buccal if IV access is unavailable). 2. **2nd Line:** Phenytoin/Fosphenytoin, Levetiracetam, or Valproate. 3. **3rd Line (Refractory):** Phenobarbital, Propofol, or Thiopental (requires intubation). * **Drug of Choice for Febrile Seizures:** Diazepam (Rectal/IV). * **Drug of Choice for Absence Seizures:** Ethosuximide (Valproate if associated with GTCS).

Q: Which mood stabilizer is used in the management of temporal lobe epilepsy?

Carbamazepine. **Explanation:** **Carbamazepine** is the drug of choice for the management of **Temporal Lobe Epilepsy (TLE)**, also known as focal seizures with impaired awareness. While it is primarily an anticonvulsant, it is a potent mood stabilizer used in Psychiatry for the treatment of Acute Mania and Prophylaxis of Bipolar Disorder, especially in patients who are non-responsive to Lithium. Its mechanism involves blocking voltage-gated sodium channels, which stabilizes hyperexcitable neuronal membranes. **Analysis of Options:** * **Valproate (Option B):** While Valproate is a broad-spectrum antiepileptic and a first-line mood stabilizer, it is typically the drug of choice for generalized tonic-clonic seizures and myoclonic seizures rather than specifically for TLE. * **Lamotrigine (Option C):** This is used primarily for the maintenance phase of Bipolar Disorder (preventing depressive episodes) and focal seizures. However, it is not the traditional "gold standard" for TLE compared to Carbamazepine. * **Lithium (Option D):** Lithium is the "gold standard" for Bipolar Affective Disorder (BPAD) but has **no anticonvulsant properties**. In fact, Lithium can lower the seizure threshold in high doses. **High-Yield Clinical Pearls for NEET-PG:** * **DOC for TLE:** Carbamazepine. * **Side Effects:** Agranulocytosis, Aplastic anemia, and **Stevens-Johnson Syndrome** (associated with the HLA-B*1502 allele). * **Enzyme Induction:** Carbamazepine is a potent **cytochrome P450 inducer**, leading to many drug-drug interactions (e.g., reducing the efficacy of oral contraceptives). * **SIADH:** It can cause hyponatremia by increasing ADH sensitivity.

Q: Which of the following agents blocks AMPA receptors?

All the above. **Explanation:** The correct answer is **D (All the above)**. This question tests the multi-modal mechanisms of action of various anti-epileptic drugs (AEDs). Glutamate is the primary excitatory neurotransmitter in the brain, acting on NMDA, AMPA, and Kainate receptors. Blocking the **AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid)** receptor reduces rapid excitatory neurotransmission, making it a key target for seizure control. * **Phenobarbitone:** While primarily known as a GABA-A receptor modulator (increasing the duration of chloride channel opening), it also inhibits excitatory transmission by blocking AMPA/Kainate receptors at higher therapeutic concentrations. * **Topiramate:** This is a "broad-spectrum" AED with multiple mechanisms: it blocks voltage-gated sodium channels, enhances GABA-A activity, inhibits carbonic anhydrase, and specifically antagonizes the **AMPA/Kainate** subtype of glutamate receptors. * **Lamotrigine:** Its primary action is blocking voltage-gated sodium channels to inhibit glutamate release. However, it also exerts inhibitory effects on postsynaptic AMPA receptors, contributing to its efficacy in both focal and generalized seizures. **Clinical Pearls for NEET-PG:** 1. **Perampanel** is the only "selective" non-competitive AMPA receptor antagonist (highly high-yield). 2. **Topiramate** is often associated with side effects like weight loss, nephrolithiasis (kidney stones), and "word-finding" difficulties (cognitive slowing). 3. **Lamotrigine** carries a Black Box Warning for Stevens-Johnson Syndrome (SJS); it must be titrated slowly. 4. **Phenobarbitone** remains the drug of choice for neonatal seizures in many traditional guidelines, though Levetiracetam is increasingly used.

Q: Which drug is contraindicated in absence seizures?

Tiagabine. Absence seizures are characterized by 3-Hz spike-and-wave discharges on EEG, resulting from oscillatory activity between the thalamus and cortex. **Tiagabine** is a selective GABA reuptake inhibitor (GAT-1 inhibitor) [1, 2, 3]. By increasing GABA concentrations in the synaptic cleft, it can paradoxically hyperpolarize thalamic neurons, leading to the activation of T-type calcium channels. This exacerbates the rhythmic discharges, potentially transforming absence seizures into **status epilepticus** or increasing their frequency [1, 2]. Other drugs that aggravate absence seizures include **Vigabatrin, Phenytoin, Carbamazepine, and Phenobarbital.** **Analysis of Incorrect Options:** * **A. Lamotrigine:** This is a broad-spectrum anticonvulsant effective against both focal and generalized seizures, including absence seizures (though usually second-line after Valproate or Ethosuximide). * **B. Clonazepam:** Benzodiazepines enhance GABA-A receptor activity. Clonazepam is effective in treating absence seizures, particularly in refractory cases, though sedation and tolerance limit its long-term use. * **D. Ethosuximide:** This is the **drug of choice** for pure absence seizures. It works by specifically inhibiting T-type $Ca^{2+}$ channels in thalamic neurons. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice (DOC) for Absence Seizures:** Ethosuximide (if only absence); Valproate (if absence is associated with GTCS). * **Drugs that worsen Absence/Myoclonic seizures:** "The Narrow Spectrum Drugs" – Phenytoin, Carbamazepine, Oxcarbazepine, Gabapentin, Tiagabine, and Vigabatrin. * **EEG Hallmark:** 3-Hz spike-and-wave pattern. * **Tiagabine Side Effect:** Can induce non-convulsive status epilepticus in patients without a history of epilepsy.

Q: Which monoclonal antibody is used in the management of Alzheimer's disease?

Bapineuzumab. Explanation: **Correct Option: C. Bapineuzumab** Alzheimer’s disease is characterized by the accumulation of **amyloid-beta (Aβ) plaques** in the brain [1]. Bapineuzumab is a humanized monoclonal antibody designed to bind to and clear these Aβ plaques. While its clinical trials showed limited efficacy in improving cognitive function, it remains the classic pharmacological example of immunotherapy targeting the amyloid cascade in Alzheimer’s pathology [2]. **Incorrect Options:** * **A. Abciximab:** This is a **Glycoprotein IIb/IIIa receptor antagonist**. It is used as an antiplatelet agent during percutaneous coronary intervention (PCI) to prevent ischemic complications. * **B. Ceolizumab (Certolizumab):** This is a **TNF-alpha inhibitor** (specifically a pegylated Fab' fragment). It is used in the management of autoimmune conditions like Crohn’s disease and Rheumatoid Arthritis. * **D. Vedolizumab:** This is an **integrin receptor antagonist** (α4β7 integrin). It is gut-selective and used primarily in the management of Inflammatory Bowel Disease (Ulcerative Colitis and Crohn’s). **High-Yield Clinical Pearls for NEET-PG:** * **Recent FDA Approvals:** While Bapineuzumab is a frequent exam option, stay updated on newer FDA-approved monoclonal antibodies for Alzheimer’s: **Aducanumab** and **Lecanemab**. * **Mechanism:** These drugs target the **Amyloid Hypothesis**, aiming to reduce the plaque burden that leads to neurodegeneration [1]. * **Side Effects:** A critical adverse effect to remember for these antibodies is **ARIA (Amyloid-Related Imaging Abnormalities)**, which includes brain edema or microhemorrhages.

Q: Which of the following conditions is a contraindication to the use of a local anesthetic agent?

Hypersensitivity to the drug. **Explanation:** **Correct Answer: D. Hypersensitivity to the drug** The only absolute contraindication among the choices is a known **hypersensitivity (allergy)** to the specific local anesthetic (LA) or its chemical class. Allergic reactions are more common with **Esters** (due to the metabolite para-aminobenzoic acid - PABA) than with **Amides**. Anaphylaxis, though rare, can be life-threatening, making hypersensitivity a definitive contraindication. **Analysis of Incorrect Options:** * **A. Parkinson’s Disease:** This is not a contraindication. While clinicians must be cautious with drug interactions (e.g., avoiding epinephrine in patients on COMT inhibitors to prevent hypertensive crises), LAs themselves do not worsen the pathology of Parkinson’s. * **B. Liver Damage:** This is a **relative contraindication/precaution**, not an absolute one. Amide LAs (like Lidocaine and Bupivacaine) are metabolized in the liver. In patients with hepatic failure, the half-life is prolonged, increasing the risk of **Systemic Toxicity (LAST)**. Dosage must be reduced, but the drugs are not strictly forbidden. * **C. Pregnancy (3rd Trimester):** LAs are frequently used for labor analgesia (Epidurals). While pregnancy increases sensitivity to LAs (requiring a dose reduction of ~30% due to engorged epidural veins and hormonal changes), it is not a contraindication. **High-Yield Clinical Pearls for NEET-PG:** * **Classification Trick:** Amides have two "i"s in their name (L**i**doca**i**ne, Bup**i**vaca**i**ne, Pr**i**loca**i**ne), while Esters have only one (Procaine, Benzocaine). * **Maximum Doses:** Lidocaine (4 mg/kg plain; 7 mg/kg with Adrenaline); Bupivacaine (2 mg/kg). * **Drug of Choice for LAST:** Intravenous **20% Lipid Emulsion** is the antidote for Local Anesthetic Systemic Toxicity. * **Prilocaine Side Effect:** Can cause **Methemoglobinemia** (treated with Methylene Blue).

Question 1

The dose of which of the following local anesthetics does NOT need to be decreased in patients with deranged liver function?

Accepted Answer

Procaine

Answer

Lignocaine

Answer

Bupivacaine

Answer

Cocaine

Question 2

What is the drug of choice for generalized tonic-clonic status epilepticus?

Accepted Answer

Lorazepam

Answer

Ethosuxamide

Answer

Sodium valproate

Answer

Lamotrigene

Question 3

Which mood stabilizer is used in the management of temporal lobe epilepsy?

Accepted Answer

Carbamazepine

Answer

Valproate

Answer

Lamotrigine

Answer

Lithium

Question 4

Which of the following agents blocks AMPA receptors?

Accepted Answer

All the above

Answer

Phenobarbitone

Answer

Topiramate

Answer

Lamotrigine

Question 5

A patient undergoing surgery was given a muscle relaxant. It produced a marked fall in blood pressure and an increase in airway resistance, which were reversed with diphenhydramine. The muscle relaxant was most probably:

Accepted Answer

Tubocurarine

Answer

Atracurium

Answer

Diazepam

Answer

Vecuronium

Question 6

Which of the following statements is TRUE regarding dental local anesthetics containing 2% lignocaine with adrenaline 1:80,000?

Accepted Answer

Dental local anesthetics containing 2% lignocaine with adrenaline 1:80,000 may cause tachycardia.

Answer

Dental local anesthetics containing 2% lignocaine with adrenaline 1:80,000 are contraindicated in patients with heart disease in any dosage.

Answer

Dental local anesthetics containing 2% lignocaine with adrenaline 1:80,000 can produce allergic reactions, in which lignocaine is usually responsible.

Answer

Dental local anesthetics containing 2% lignocaine with adrenaline 1:80,000 or even prilocaine with felypressin should not be used in the pregnant patient because of the oxytocic effects of adrenaline or felypressin.

Question 7

Which drug is contraindicated in absence seizures?

Accepted Answer

Tiagabine

Answer

Lamotrigine

Answer

Clonazepam

Answer

Ethosuximide

Question 8

A patient developed nausea, vomiting, tingling, and numbness in the fingertips, which also turned blue, after taking a drug for an acute attack of migraine. Which of the following drugs is most likely implicated in causing these findings?

Accepted Answer

Dihydroergotamine

Answer

Sumatriptan

Answer

Aspirin

Answer

Butorphanol

Question 9

Which monoclonal antibody is used in the management of Alzheimer's disease?

Accepted Answer

Bapineuzumab

Answer

Abciximab

Answer

Ceolizumab

Answer

Vedolizumab

Question 10

Which of the following conditions is a contraindication to the use of a local anesthetic agent?

Accepted Answer

Hypersensitivity to the drug

Answer

Parkinson's disease

Answer

Liver damage

Answer

Pregnancy (3rd trimester)

Central Nervous System Pharmacology — MCQs

Central Nervous System Pharmacology — MCQs

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