Central Nervous System Pharmacology Practice Questions

Q: A patient took a drug for migraine treatment, following which there was numbness, and his hand appeared as below. What is the possible drug that was taken?

Dihydroergotamine. ***Dihydroergotamine*** - Dihydroergotamine is an **ergot alkaloid** that causes potent, non-selective **vasoconstriction** of both arteries and veins. This can lead to severe peripheral ischemia, a condition known as **ergotism**. - The clinical presentation of numbness, tingling, and cold extremities, as suggested by the patient's symptoms and the appearance of the hand, is a classic manifestation of ergotamine-induced vasospasm. *Sumatriptan* - Sumatriptan is a **triptan**, which is a selective **5-HT1B/1D receptor agonist**. While it does cause vasoconstriction, its effects are more selective for **cranial arteries**. - Though it can cause paresthesias (tingling/numbness), severe peripheral ischemia leading to the signs seen in the image is a much rarer side effect compared to ergot alkaloids. *Butorphanol* - Butorphanol is an **opioid agonist-antagonist** used for pain relief. Its mechanism of action does not involve vasoconstriction. - Common side effects are related to the central nervous system, such as sedation, dizziness, and nausea, not peripheral vascular symptoms. *Aspirin* - Aspirin is a **nonsteroidal anti-inflammatory drug (NSAID)** that inhibits **cyclooxygenase (COX)** and has antiplatelet effects. It does not cause vasoconstriction. - Its primary side effects include **gastrointestinal irritation** and an increased risk of **bleeding**, which are unrelated to the patient's presentation.

Q: Which anti-epileptic drug is commonly associated with gum hypertrophy and dizziness as side effects?

Phenytoin. ***Phenytoin*** - It is classically associated with **gingival hyperplasia** (gum hypertrophy) due to increased stimulation of **fibroblast activity** and **collagen synthesis** in the gingiva, which is a major distinction from other AEDs. - Dose-dependent **dizziness** and **ataxia** are very common CNS side effects, reflecting its non-linear kinetics and narrow therapeutic index. *Carbamazepine* - Its most characteristic serious side effects include **aplastic anemia** and agranulocytosis, requiring baseline and periodic complete blood counts (CBCs). - It is a potent inducer of **CYP450 enzymes** and frequently causes **hyponatremia** (via Syndrome of Inappropriate Antidiuretic Hormone secretion, SIADH). *Levetiracetam* - This drug is generally well-tolerated but is notably associated with significant **behavioral side effects** such as irritability, aggression, and mood instability. - It does not cause **gum hypertrophy** or significant liver enzyme induction, unlike Phenytoin or Carbamazepine. *Topiramate* - Commonly causes side effects related to cognition, often called **"Dopamax"**, leading to cognitive slowing, difficulty concentrating, and language problems. - Other unique side effects include **weight loss** and the formation of **kidney stones** (nephrolithiasis) due to inhibition of carbonic anhydrase.

Q: What is the mechanism of action of Ethosuximide?

Inhibits calcium channels in thalamic neurons. ***Inhibits calcium channels in thalamic neurons***- Ethosuximide selectively blocks **T-type calcium channels** (**transient type**) primarily found on **thalamic neurons**.- This blockade reduces the **low-threshold burst firing** responsible for the characteristic **3-Hz spike-and-wave discharge** seen in absence seizures.*Enhances GABAergic inhibition*- This mechanism is characteristic of **Benzodiazepines** and **Barbiturates**, which increase the frequency or duration of GABA-A channel opening.- While some broad-spectrum AEDs like **Valproate** also increase GABA levels, this is not the primary mechanism of action for Ethosuximide.*Blocks sodium channels*- Drugs that block neuronal sodium channels, such as **Phenytoin** and **Carbamazepine**, are effective against tonic-clonic and partial seizures.- This mechanism prevents the rapid, sustained firing of action potentials but is largely ineffective against the burst firing characteristic of absence seizures.*Increases serotonin levels*- This is the primary mechanism associated with **Selective Serotonin Reuptake Inhibitors (SSRIs)** and other antidepressants.- It is not relevant to the function of Ethosuximide, which is specific to modulating neuronal excitability through calcium channels.

Q: Which of the following anti-epileptics is not given during pregnancy?

Valproate. ***Correct: Valproate*** - Valproate (Valproic Acid) is the anti-epileptic drug (AED) with the **highest teratogenic risk**, particularly causing **Neural Tube Defects (NTDs)** like spina bifida (1-2% risk), in a dose-dependent manner - It is **strictly contraindicated** during pregnancy (FDA Category X) due to increased risks of **major congenital malformations (10-20%)** and long-term neurodevelopmental consequences, including lower IQ and increased risk of **Autism Spectrum Disorder** in the child - This is the AED that should **NOT be given during pregnancy** *Incorrect: Lamotrigine* - Lamotrigine is generally considered one of the **safer AEDs** used in pregnancy, often a preferred alternative when monotherapy is necessary - While initial data suggested a small risk of oral clefts, current extensive evidence shows it has a **low overall risk** of major congenital malformations - Can be safely used during pregnancy when needed *Incorrect: Levetiracetam* - Levetiracetam (Keppra) is highly favored during pregnancy because it has one of the **lowest risks** of causing major congenital malformations among all AEDs - It is often recommended as the **drug of choice** for women who require AED continuation during gestation due to its favorable safety profile for both physical and neurodevelopmental outcomes *Incorrect: Carbamazepine* - Carbamazepine increases the risk of teratogenicity, classically associated with a risk of **NTDs** (~1%, lower than Valproate) and minor craniofacial defects like cleft lip/palate - Although generally reserved for situations where safer alternatives are ineffective, it **can still be used** when benefits outweigh risks - not absolutely contraindicated like valproate

Q: For benzodiazepines and barbiturates, which of the following is true?

Both have effect on GABA-A chloride channel. ***Both have effect on GABA-A chloride channel*** Both benzodiazepines and barbiturates act as **positive allosteric modulators** of the **GABA-A receptor**, a **ligand-gated chloride channel**, leading to increased frequency (BZDs) or duration (Barbiturates) of channel opening [1]. This enhancement of the inhibitory neurotransmitter GABA results in **CNS depression**, which is the basis for their anxiolytic, sedative, and hypnotic effects [1].***Flumazenil is the antidote for barbiturate*** **Flumazenil** is a competitive antagonist used specifically to reverse the effects of **benzodiazepines** by blocking their binding site on the GABA-A receptor [1]. There is **no specific pharmacological antidote** for barbiturate overdose; management involves supportive care like airway protection and respiratory support.***Cause additive sedation with alcohol*** Although both drugs cause severe **synergistic CNS depression** when combined with alcohol, this is a property shared by many CNS depressants, not unique to this pair, whereas their shared molecular target (D) is a fundamental defining characteristic. The combination of either BZDs or barbiturates with ethanol significantly **potentiates sedation** and increases the risk of respiratory depression and coma.***Thiopentone has short duration of action due to metabolism*** The ultra-short action of **thiopentone** following a single intravenous dose is primarily due to rapid **redistribution** out of the brain into highly perfused tissues (muscle and fat) since it is highly lipid-soluble [1, 2]. While it is eventually metabolized by the liver, **hepatic metabolism** is not the factor responsible for the swift onset and termination of its hypnotic effect [1].

Q: A woman diagnosed with migraine has a family history of coronary artery disease. What is the drug of choice for migraine prophylaxis?

Propranolol. ***Propranolol*** - **Propranolol** is a first-line drug for migraine prophylaxis, particularly favored in patients with co-existing conditions like hypertension, anxiety, or, as in this case, risk factors for **Coronary Artery Disease (CAD)**. - As a non-selective beta-blocker, it provides effective migraine prevention while potentially offering **cardioprotective benefits**, making it the safest and best choice here. *Topiramate* - **Topiramate** is also a first-line prophylactic agent, but it is often preferred when patients need to avoid weight gain or have co-existing seizure disorders. - It has no particular advantage over propranolol in lowering cardiac risk and is associated with common side effects such as cognitive impairment (**'fogginess'**) and **nephrolithiasis**. *Ergotamine* - **Ergotamine preparations** are severe vasoconstrictors and are used primarily for the **acute termination** of migraine attacks, not for long-term prophylaxis. - They are absolutely **contraindicated** in patients with established or high risk of **Coronary Artery Disease** (CAD) due to the risk of **myocardial infarction** and stroke. *Amitriptyline* - **Amitriptyline** (a TCA) is used for prophylaxis, especially in patients with co-existing **insomnia** or chronic **tension headaches**. - While effective, TCAs can have potential **cardiac side effects** (e.g., QTc prolongation, orthostatic hypotension) which makes **propranolol** a medically safer choice for patients with a family history of CAD.

Q: Sodium thiopentone is regarded as an ultrashort-acting drug due to

Rapid redistribution. ***Rapid redistribution*** - The ultrashort action of **thiopentone** is primarily due to its rapid **redistribution** from the central compartment (brain) to peripheral tissues (muscle and fat). - This rapid drop in plasma and brain concentration leads to swift termination of the drug's hypnotic effect. *Metabolism* - While thiopentone is metabolized primarily by the **liver**, its metabolic clearance is relatively slow, contributing to its long elimination half-life rather than its quick onset/offset. *Excretion* - Thiopentone is only minimally excreted unchanged by the **kidneys**; renal excretion is not the reason for the ultrashort duration of action. *Short elimination half-life* - Thiopentone actually has a **long elimination half-life** (around 10–12 hours) because of its high lipid solubility, long protein binding, and slow systemic metabolism. - The duration of action is governed by redistribution, not by the elimination half-life.

Q: The application of the following product can lead to development of: (Recent NEET Pattern 2016-17)

Methemoglobinemia. ***Methemoglobinemia (Correct)*** - EMLA cream contains **lidocaine** and **prilocaine**, both of which are **amide-type local anesthetics** - Prilocaine, in particular, can cause methemoglobinemia due to its metabolite, **o-toluidine**, which oxidizes hemoglobin to methemoglobin - While methemoglobinemia is rare with proper use, it is a known and serious adverse effect, especially when applied to large areas, on broken skin, or in infants - This is the most specific adverse effect associated with prilocaine in EMLA cream *Seizures (Incorrect)* - Seizures are a known systemic toxicity of local anesthetics like lidocaine and prilocaine but are usually associated with **very high systemic concentrations**, often from accidental intravenous injection or excessive application over large areas - While possible with overdose, methemoglobinemia is a more specific and direct concern linked to prilocaine's metabolic pathway - CNS toxicity typically requires systemic absorption beyond what occurs with proper topical use *Depression (Incorrect)* - Depression is **not a direct or common adverse effect** of EMLA cream or its components - Systemic absorption of local anesthetics can cause central nervous system effects, but depression is generally not among them - CNS effects more commonly involve excitation (restlessness, tremors) or sedation depending on the dose *Hypertension (Incorrect)* - Local anesthetics generally cause **vasodilation** at therapeutic doses, potentially leading to **hypotension** rather than hypertension, especially with systemic absorption - Hypertension is not a characteristic side effect associated with the topical application of EMLA cream - The cardiovascular effects of local anesthetics, when present, typically involve decreased blood pressure and myocardial depression

Question 1

A patient took a drug for migraine treatment, following which there was numbness, and his hand appeared as below. What is the possible drug that was taken?

Accepted Answer

Dihydroergotamine

Answer

Sumatriptan

Answer

Aspirin

Answer

Butorphanol

Question 2

Which anti-epileptic drug is commonly associated with gum hypertrophy and dizziness as side effects?

Accepted Answer

Phenytoin

Answer

Carbamazepine

Answer

Topiramate

Answer

Levetiracetam

Question 3

What is the mechanism of action of Ethosuximide?

Accepted Answer

Inhibits calcium channels in thalamic neurons

Answer

Enhances GABAergic inhibition

Answer

Blocks sodium channels

Answer

Increases serotonin levels

Question 4

Which of the following statements is not true regarding benzodiazepines and barbiturates?

Accepted Answer

Flumazenil can be used for severe alcohol withdrawal symptoms

Answer

Both can be used as a sedative hypnotic

Answer

With alcohol it causes CNS depression

Answer

Both act on GABA-A

Question 5

Which of the following anti-epileptics is not given during pregnancy?

Accepted Answer

Valproate

Answer

Lamotrigine

Answer

Carbamazepine

Answer

Levetiracetam

Question 6

For benzodiazepines and barbiturates, which of the following is true?

Accepted Answer

Both have effect on GABA-A chloride channel

Answer

Flumazenil is the antidote for barbiturate

Answer

Cause additive sedation with alcohol

Answer

Thiopentone has short duration of action due to metabolism

Question 7

Which of the following statements is incorrect?

Accepted Answer

Cannabis use can result in self-driven, repetitive behaviours

Answer

Alcohol in low dose causes brain stimulation and in higher doses, causes brain suppression

Answer

Opioids are very effective analgesics

Answer

Volatile inhalational agents (when abused) are mostly toxic to humans

Question 8

A woman diagnosed with migraine has a family history of coronary artery disease. What is the drug of choice for migraine prophylaxis?

Accepted Answer

Propranolol

Answer

Topiramate

Answer

Ergotamine

Answer

Amitriptyline

Question 9

Sodium thiopentone is regarded as an ultrashort-acting drug due to

Accepted Answer

Rapid redistribution

Answer

Short elimination half-life

Answer

Metabolism

Answer

Excretion

Question 10

The application of the following product can lead to development of: (Recent NEET Pattern 2016-17)

Accepted Answer

Methemoglobinemia

Answer

Seizures

Answer

Depression

Answer

Hypertension

Central Nervous System Pharmacology — MCQs

Central Nervous System Pharmacology — MCQs

On this page

Practice by Chapter

Want unlimited practice?