Central Nervous System Pharmacology Practice Questions

Q: Use of ergotamine is contraindicated in which of the following conditions?

Ischemic heart disease. **Explanation:** **Ergotamine** is an ergot alkaloid that acts as a potent, non-selective agonist at **5-HT1B/1D receptors**. Its primary therapeutic effect in migraine management is mediated through **intense peripheral and cranial vasoconstriction**. **1. Why Ischemic Heart Disease (IHD) is the Correct Answer:** The vasoconstrictive action of ergotamine is not limited to cranial vessels; it also affects the coronary arteries. In patients with IHD, ergotamine can precipitate **coronary vasospasm**, leading to myocardial ischemia, angina, or even myocardial infarction. Therefore, it is strictly contraindicated in IHD, peripheral vascular disease (Raynaud's), and uncontrolled hypertension. **2. Analysis of Incorrect Options:** * **Diabetes Mellitus:** While DM is a risk factor for vascular disease, it is not a direct contraindication unless the patient has documented macrovascular complications (like CAD or PVD). * **Anemia:** There is no direct pharmacological interaction or contraindication between ergotamine use and anemia. * **Postpartum Hemorrhage (PPH):** Ergot derivatives (specifically **Methylergometrine**) are actually *indicated* in PPH to promote uterine contraction. While ergotamine itself is not the first-line ergot for PPH, it is not contraindicated. **3. High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** 5-HT1B/1D agonist → Vasoconstriction + inhibition of neurogenic inflammation. * **Ergotism (St. Anthony’s Fire):** Toxicity characterized by severe peripheral ischemia (gangrene) and CNS stimulation (hallucinations). * **Drug Interaction:** Ergotamine metabolism is inhibited by **CYP3A4 inhibitors** (e.g., Ritonavir, Erythromycin), which can lead to life-threatening ischemia. * **Triptans vs. Ergots:** Both are contraindicated in IHD due to coronary vasoconstriction.

Q: All of the following are true about Triptans except:

They act by inhibiting 5HT 1B / 1D receptors.. The core mechanism of Triptans involves **agonism**, not inhibition. Triptans are selective **5-HT$_{1B/1D}$ receptor agonists** [1, 2]. Their therapeutic effect in migraine is mediated through three mechanisms:1. **Vasoconstriction:** Activation of 5-HT$_{1B}$ receptors on intracranial blood vessels reverses vasodilation [1].2. **Neuropeptide Inhibition:** Activation of 5-HT$_{1D}$ receptors on trigeminal nerve endings inhibits the release of pro-inflammatory peptides (like CGRP and Substance P) [2].3. **Central Inhibition:** They inhibit pain transmission in the trigeminal nucleus caudalis.#### Analysis of Options:* **Option D (Correct):** This is the false statement. Triptans **stimulate** (act as agonists) rather than inhibit these receptors.* **Option A:** Triptans are indeed the **Drug of Choice (DOC)** for moderate-to-severe acute migraine attacks when NSAIDs fail [1].* **Option B:** **Frovatriptan** has the longest half-life (~26 hours), making it useful for preventing menstrual migraine [3].* **Option C:** **Sumatriptan** is the prototype and is available via oral, nasal, and **subcutaneous** routes [1, 3]. The SC route offers the fastest onset of action (approx. 10–15 mins) [3].#### High-Yield NEET-PG Pearls:* **Fastest acting triptan:** Rizatriptan (oral) or Sumatriptan (SC) [3].* **Contraindications:** Since they cause vasoconstriction, they are strictly contraindicated in patients with **Ischemic Heart Disease (IHD)**, Prinzmetal angina, and uncontrolled hypertension [3].* **Sumatriptan** has the lowest oral bioavailability among the group.* **Almotriptan** has the best oral bioavailability.

Q: Baclofen is used in which of the following conditions?

Spasticity. **Explanation:** **Baclofen** is a centrally acting skeletal muscle relaxant that acts as a selective **GABA-B receptor agonist**. It works by increasing potassium conductance, leading to hyperpolarization of neurons. This inhibits both monosynaptic and polysynaptic reflexes at the spinal cord level, effectively reducing muscle tone and frequency of spasms. * **Why Spasticity is Correct:** Baclofen is the drug of choice for managing **spasticity** associated with spinal cord injuries, multiple sclerosis, and amyotrophic lateral sclerosis (ALS). It is preferred because it causes less sedation compared to benzodiazepines. **Analysis of Incorrect Options:** * **Parkinsonism:** This is a movement disorder caused by dopamine deficiency in the nigrostriatal pathway. Treatment involves dopaminergic agents (Levodopa) or anticholinergics, not GABA agonists. * **Epilepsy:** Baclofen is generally **avoided** in patients with epilepsy as it can lower the seizure threshold and potentially worsen the condition. * **Stroke:** While stroke can lead to spasticity (upper motor neuron lesion), Baclofen is less effective for spasticity of cerebral origin compared to spinal origin. Furthermore, it is not a primary treatment for the stroke itself. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** GABA-B agonist (G-protein coupled receptor). * **Administration:** Can be given orally or via an **intrathecal pump** for severe refractory spasticity. * **Withdrawal Warning:** Abrupt discontinuation of Baclofen can lead to life-threatening withdrawal symptoms, including hallucinations, seizures, and rebound spasticity. * **Comparison:** Unlike Dantrolene (which acts directly on the muscle/Ryanodine receptors), Baclofen acts on the **spinal cord**.

Q: Which of the following effects is specifically observed with intravenous diazepam and not with other routes of administration?

Coronary dilatation. **Explanation:** The correct answer is **Coronary dilatation**. **Why it is correct:** Intravenous (IV) diazepam is formulated in a solvent called **propylene glycol** because diazepam is poorly soluble in water. When administered intravenously, this solvent—rather than the diazepam molecule itself—exerts a direct vasodilatory effect on the coronary arteries. This specific hemodynamic effect is unique to the IV route and is not observed when the drug is administered orally or intramuscularly. **Analysis of incorrect options:** * **A. Analgesia:** Benzodiazepines (BZDs) like diazepam do not possess analgesic properties. They are used for sedation, anxiolysis, and muscle relaxation, but they do not act on opioid receptors or inhibit pain pathways. * **B. Sedation:** Sedation is the primary pharmacological effect of diazepam regardless of the route (Oral, IV, or Rectal). It is not specific to the intravenous route. * **C. Hypotension:** While rapid IV injection of diazepam can cause a transient drop in blood pressure due to peripheral vasodilation (also partly due to propylene glycol), it is less characteristic and less specific than the coronary dilatation effect often highlighted in pharmacological literature. **High-Yield Clinical Pearls for NEET-PG:** * **Propylene Glycol Toxicity:** High doses of IV diazepam or lorazepam can lead to propylene glycol toxicity, manifesting as anion gap metabolic acidosis and acute kidney injury. * **Injection Site:** IV diazepam is notorious for causing **thrombophlebitis** (painful inflammation of the vein) due to the propylene glycol solvent. * **Drug of Choice:** While diazepam was historically the drug of choice for **Status Epilepticus**, current protocols often prefer **Lorazepam** (IV) due to its longer duration of action in the brain. * **Antidote:** The specific antagonist for benzodiazepine overdose is **Flumazenil**.

Q: Which of the following drugs is not metabolized by the liver?

Oxazepam. **Explanation:** The metabolism of Benzodiazepines (BZDs) primarily occurs via two phases in the liver: **Phase I (Oxidation)** by Cytochrome P450 enzymes and **Phase II (Conjugation)** with glucuronic acid. **Why Oxazepam is the correct answer:** Most BZDs undergo Phase I oxidation to form active metabolites, which significantly prolongs their duration of action. However, a specific group of BZDs—**Oxazepam, Temazepam, and Lorazepam (mnemonic: OTL)**—bypass Phase I oxidation entirely. They undergo direct **Phase II glucuronidation** to form inactive, water-soluble metabolites that are excreted by the kidneys. Because they do not rely on the CYP450 system, they are the drugs of choice in patients with **liver failure** or the **elderly**, where oxidative capacity is diminished. **Analysis of Incorrect Options:** * **Diazepam:** A long-acting BZD that undergoes extensive Phase I metabolism to form active metabolites like desmethyldiazepam (nordiazepam), giving it a very long half-life. * **Flunitrazepam & Nitrazepam:** These are nitro-benzodiazepines. They undergo Phase I reduction and acetylation in the liver before excretion. **NEET-PG High-Yield Pearls:** 1. **OTL (Oxazepam, Temazepam, Lorazepam):** "Outside The Liver" (mnemonic for bypassing Phase I). Safe in cirrhosis and elderly patients. 2. **Active Metabolites:** Diazepam and Chlordiazepoxide have the longest-acting active metabolites. 3. **Enzyme Inhibition:** Drugs like Cimetidine or Erythromycin inhibit CYP450 and can increase the toxicity of Diazepam, but they do **not** affect the clearance of Oxazepam or Lorazepam.

Q: Which of the following does NOT affect the duration of action of local anesthesia?

Non-nervous tissue diffusibility. The duration of action of a local anesthetic (LA) is primarily determined by how long the drug remains in contact with the nerve membrane. This is governed by its chemical properties and local blood flow. ### **Why "Non-nervous tissue diffusibility" is the Correct Answer** Non-nervous tissue diffusibility (or the **pKa/Ionization constant**) primarily determines the **onset of action**, not the duration. A drug’s ability to diffuse through non-neural tissues relates to how quickly it reaches the target nerve. Once the drug is at the nerve, its persistence there (duration) depends on binding and vascular removal, not initial tissue diffusion. ### **Analysis of Incorrect Options** * **Protein Binding (Option A):** This is the **most important** determinant of duration. LAs bind to proteins (like albumin and alpha-1 acid glycoprotein) in the sodium channel. High protein binding (e.g., Bupivacaine, Ropivacaine) results in a longer duration of action compared to low protein binding (e.g., Lidocaine). * **Addition of a Vasoconstrictor (Option B):** Adding Epinephrine causes local vasoconstriction, which decreases the rate of systemic absorption (washout). This keeps the LA at the nerve site longer, thereby increasing the duration. * **Vasodilator Activity (Option C):** Most LAs (except Cocaine and Ropivacaine) are intrinsic vasodilators. Higher intrinsic vasodilatory activity increases blood flow, leading to faster systemic absorption and a **shorter** duration of action. ### **High-Yield NEET-PG Pearls** * **Potency** is determined by **Lipid Solubility**. * **Onset of Action** is determined by **pKa** (Lower pKa = more non-ionized drug = faster onset). * **Duration of Action** is determined by **Protein Binding**. * **Bupivacaine** has the highest protein binding (~95%) and thus a very long duration. * **Cocaine** is the only LA that causes significant vasoconstriction.

Q: Which serotonin-norepinephrine reuptake inhibitor is predominantly used in the condition shown above?

Duloxetine. ***Duloxetine*** - **FDA-approved** specifically for **fibromyalgia** treatment, making it the preferred SNRI for this condition with proven efficacy in clinical trials. - Works by inhibiting both **serotonin and norepinephrine reuptake**, providing dual mechanism for **pain relief** and **mood stabilization** in fibromyalgia patients. *Venlafaxine* - While it is an **SNRI**, it is **not specifically FDA-approved** for fibromyalgia treatment, unlike duloxetine. - Primarily indicated for **depression** and **anxiety disorders**, with less established evidence for fibromyalgia pain management. *Citalopram* - This is a **selective serotonin reuptake inhibitor (SSRI)**, not an SNRI, making it the wrong drug category. - Lacks the **norepinephrine reuptake inhibition** component that is beneficial for **neuropathic pain** management in fibromyalgia. *Escitalopram* - Also an **SSRI**, not an SNRI, so it doesn't fit the question's requirement for a serotonin-norepinephrine reuptake inhibitor. - Primarily used for **depression** and **anxiety disorders** without specific indication for fibromyalgia pain relief.

Question 1

Use of ergotamine is contraindicated in which of the following conditions?

Accepted Answer

Ischemic heart disease

Answer

Diabetes Mellitus

Answer

Anemia

Answer

Postpartum hemorrhage

Question 2

All of the following are true about Triptans except:

Accepted Answer

They act by inhibiting 5HT 1B / 1D receptors.

Answer

They are the drug of choice in the acute attack of migraine.

Answer

Frovatriptan is the longest acting triptan.

Answer

Sumatriptan can also be given subcutaneously.

Question 3

Baclofen is used in which of the following conditions?

Accepted Answer

Spasticity

Answer

Parkinsonism

Answer

Epilepsy

Answer

Stroke

Question 4

All of the following statements about phenytoin are true except:

Accepted Answer

Cerebellar degeneration occurs on long-term administration

Answer

It follows saturation kinetics

Answer

Anti-seizure activity closely resembles plasma concentration

Answer

Does not depress CNS

Question 5

Lorazepam is preferred over Diazepam in the treatment of status epilepticus because:

Accepted Answer

It has a more sustained action due to lower lipid solubility and slower distribution.

Answer

It has a longer half-life than diazepam.

Answer

It has faster clearance.

Answer

It has more bioavailability.

Question 6

Which of the following effects is specifically observed with intravenous diazepam and not with other routes of administration?

Accepted Answer

Coronary dilatation

Answer

Analgesia

Answer

Sedation

Answer

Hypotension

Question 7

Which of the following drugs is not metabolized by the liver?

Accepted Answer

Oxazepam

Answer

Flunitrazepam

Answer

Diazepam

Answer

Nitrazepam

Question 8

Which of the following does NOT affect the duration of action of local anesthesia?

Accepted Answer

Non-nervous tissue diffusibility

Answer

Protein binding capacity of the local anesthetic

Answer

Addition of a vasoconstrictor

Answer

Vasodilator activity of the local anesthetic

Question 9

Which serotonin-norepinephrine reuptake inhibitor is predominantly used in the condition shown above?

Accepted Answer

Duloxetine

Answer

Venlafaxine

Answer

Citalopram

Answer

Escitalopram

Question 10

All of the following drugs are used for managing status epilepticus except?

Accepted Answer

Carbamazepine

Answer

Phenytoin

Answer

Diazepam

Answer

Thiopentone sodium

Central Nervous System Pharmacology — MCQs

Central Nervous System Pharmacology — MCQs

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