Central Nervous System Pharmacology Practice Questions

Q: Buspirone is used as a/an?

Anxiolytic. **Explanation:** Buspirone is a unique non-benzodiazepine drug used primarily as an **anxiolytic**. Its mechanism of action involves acting as a **selective partial agonist at the 5-HT1A receptors** in the brain. Unlike benzodiazepines, it does not interact with the GABA-A receptor complex, which accounts for its distinct clinical profile. **Why the other options are incorrect:** * **Sedative:** Buspirone lacks sedative properties. It does not cause significant drowsiness or cognitive impairment, making it suitable for patients who need to remain alert. * **Muscle relaxant:** It has no effect on skeletal muscle tone, unlike benzodiazepines (e.g., Diazepam), which act on spinal GABA receptors to reduce spasticity. * **Anticonvulsant:** Buspirone does not possess anti-seizure activity and cannot be used in the management of epilepsy or status epilepticus. **High-Yield Clinical Pearls for NEET-PG:** * **Slow Onset:** Unlike benzodiazepines, Buspirone has a delayed onset of action (taking **1–2 weeks** to show effects). It is used for Generalized Anxiety Disorder (GAD) but is **ineffective for acute anxiety or panic attacks**. * **Lack of Dependence:** It has **no potential for abuse**, no withdrawal symptoms, and does not potentiate the effects of alcohol. * **Side Effects:** Common side effects include dizziness, nausea, and headache. It does not cause psychomotor impairment (no "hangover" effect). * **Metabolism:** It is metabolized by **CYP3A4**; therefore, its levels can be increased by grapefruit juice or erythromycin.

Q: Which of the following drugs can be used as a transcranial patch for the treatment of parkinsonism?

Rotigotine. **Explanation:** **Rotigotine** is a non-ergot dopamine agonist (D2, D3, and D1 receptor stimulator) specifically designed for **transdermal delivery**. It is highly lipophilic, allowing it to be formulated as a once-daily **transdermal patch**. This delivery method provides continuous drug delivery over 24 hours, maintaining stable plasma levels and avoiding the "pulsatile" stimulation of dopamine receptors associated with oral medications, which helps in reducing motor fluctuations in Parkinson’s disease. **Analysis of Incorrect Options:** * **Levodopa (A):** It is the precursor of dopamine and the most effective drug for Parkinsonism. However, it has a short half-life and requires active transport across the gut and blood-brain barrier; it is not available as a patch. * **Apomorphine (C):** A potent dopamine agonist used as "rescue therapy" for acute "off" episodes. Due to extensive first-pass metabolism, it cannot be given orally. It is administered via **subcutaneous injection** or continuous infusion, not a patch. * **Aprantine (D):** This is a distractor. It is not a recognized drug for the treatment of Parkinson’s disease. **High-Yield Clinical Pearls for NEET-PG:** * **Rotigotine Patch:** Useful for patients with dysphagia or those requiring stable nocturnal symptom control. * **Dopamine Agonists:** Divided into Ergot (Bromocriptine, Pergolide) and Non-ergot (Pramipexole, Ropinirole, Rotigotine). Non-ergot derivatives are preferred due to the lack of risk for cardiac valvular fibrosis. * **Side Effects:** Like other dopamine agonists, Rotigotine can cause impulse control disorders (pathological gambling, hypersexuality) and sudden sleep attacks.

Q: A 10-year-old boy presents with difficulty in learning at school. He experiences short lapses of awareness with eyelid fluttering every 5–10 minutes. EEG studies reveal brief 3 Hz spike and wave discharges appearing synchronously in all leads. Which of the following drugs would be effective but has the disadvantage that it causes sedation and tolerance?

Clonazepam. **Explanation:** The clinical presentation of short lapses of awareness, eyelid fluttering, and the characteristic **3 Hz spike-and-wave discharges** on EEG is diagnostic of **Absence Seizures (Petit Mal)**. **Why Clonazepam is the correct answer:** While Ethosuximide and Valproate are the preferred first-line treatments for absence seizures, the question specifically asks for a drug that is effective but limited by **sedation and the development of tolerance**. **Clonazepam**, a benzodiazepine, fits this profile perfectly. It is highly effective in suppressing absence seizures but is rarely used as a first-line agent because patients quickly develop tolerance to its anti-seizure effects, and it causes significant CNS depression (sedation). **Analysis of Incorrect Options:** * **Ethosuximide (B):** This is the drug of choice for pure absence seizures. It works by blocking T-type Ca²⁺ channels. It does *not* typically cause significant tolerance. * **Valproic acid (D):** The drug of choice for absence seizures associated with generalized tonic-clonic seizures (GTCS). While it has side effects (hepatotoxicity, weight gain), tolerance is not a primary clinical concern. * **Diazepam (A):** While a benzodiazepine, it is primarily used for the acute management of Status Epilepticus (IV) or febrile seizures (rectal). It is not used for the long-term maintenance therapy of absence seizures. **High-Yield NEET-PG Pearls:** * **DOC for Absence Seizures:** Ethosuximide (if pure); Valproate (if mixed with GTCS). * **Mechanism of Ethosuximide:** Inhibition of T-type Calcium channels in thalamic neurons. * **Drugs that Aggravate Absence Seizures:** Phenytoin, Carbamazepine, and Vigabatrin. * **Benzodiazepine Limitation:** The main drawback of using BDZs like Clonazepam or Nitrazepam in chronic epilepsy is **tolerance** (downregulation of GABA-A receptors).

Q: Which of the following is NOT a feature of opioid intake?

Dilated pupils. **Explanation:** The correct answer is **D. Dilated pupils**. Opioids are central nervous system (CNS) depressants that typically cause **miosis** (pinpoint pupils), not dilation. **1. Why "Dilated Pupils" is the correct choice:** Opioids stimulate the **Edinger-Westphal nucleus** of the oculomotor nerve (CN III), leading to parasympathetic overactivity and constriction of the pupil (miosis). This is a hallmark sign of opioid use and overdose. In contrast, dilated pupils (mydriasis) are usually seen during **opioid withdrawal** or in specific cases like Pethidine (Meperidine) toxicity, which has atropine-like anticholinergic effects. **2. Why the other options are incorrect:** * **A & B (Relaxation and Euphoria):** Opioids act on **mu (μ) receptors** in the reward pathway of the brain (ventral tegmental area and nucleus accumbens), leading to a sense of well-being, detachment from anxiety, and intense pleasure. * **C (Analgesia):** This is the primary therapeutic effect of opioids. They inhibit the transmission of pain signals in the spinal cord and alter the perception of pain in the higher cortical centers. **High-Yield Clinical Pearls for NEET-PG:** * **The Triad of Opioid Overdose:** Coma, Pinpoint pupils, and Respiratory depression. * **Tolerance:** Tolerance develops to most effects (analgesia, euphoria, respiratory depression) **EXCEPT** for miosis and constipation. These two signs remain even in chronic users. * **Exception to Miosis:** **Pethidine** causes mydriasis due to its antimuscarinic action. * **Antidote:** **Naloxone** is the drug of choice for acute opioid poisoning (short-acting IV antagonist).

Q: Natalizumab is used in the treatment of which condition?

Multiple sclerosis. **Explanation:** **Natalizumab** is a humanized monoclonal antibody that targets the **$\alpha$4-integrin** (VLA-4) subunit. Its primary mechanism involves blocking the interaction between $\alpha$4-integrin on the surface of leukocytes and **VCAM-1** (Vascular Cell Adhesion Molecule-1) on vascular endothelial cells. By inhibiting this adhesion, it prevents leukocytes from crossing the blood-brain barrier and entering the Central Nervous System (CNS), thereby reducing the inflammatory destruction of myelin in **Multiple Sclerosis (MS)**. It is also used in Crohn’s disease. **Analysis of Incorrect Options:** * **B. Breast Carcinoma:** Treatment typically involves Trastuzumab (anti-HER2) or Pertuzumab, not Natalizumab. * **C. Psoriasis:** Common biologics used include Infliximab (anti-TNF$\alpha$), Ustekinumab (anti-IL-12/23), or Secukinumab (anti-IL-17A). * **D. B-cell Lymphoma:** Rituximab (anti-CD20) is the classic monoclonal antibody used for this condition. **High-Yield Clinical Pearls for NEET-PG:** * **PML Risk:** The most significant adverse effect of Natalizumab is **Progressive Multifocal Leukoencephalopathy (PML)**, caused by the reactivation of the **JC virus**. Patients must be screened for JC virus antibodies before starting therapy. * **Mechanism Mnemonic:** Natalizumab "prevents **N**eutrophils/leukocytes from **A**dhering" to the endothelium. * **FDA Indication:** It is generally reserved as a second-line therapy for relapsing-remitting MS due to the risk of PML.

Q: Which antiepileptic drug does not act via inhibition of sodium channels?

Vigabatrin. **Explanation:** The correct answer is **Vigabatrin**. **1. Mechanism of Vigabatrin (Correct Answer):** Vigabatrin is a structural analog of GABA that acts as an **irreversible inhibitor of GABA-transaminase (GABA-T)**, the enzyme responsible for the degradation of GABA. By inhibiting this enzyme, it increases the concentration of GABA (the primary inhibitory neurotransmitter) in the synaptic cleft. It does not have any significant activity on voltage-gated sodium channels. **2. Analysis of Incorrect Options (Sodium Channel Blockers):** * **Phenytoin:** A classic example of a drug that blocks voltage-gated sodium channels in their inactive state, preventing high-frequency repetitive firing of action potentials. * **Carbamazepine:** Similar to phenytoin, it stabilizes the inactivated state of sodium channels. It is the drug of choice for trigeminal neuralgia. * **Lamotrigine:** A newer antiepileptic that blocks sodium channels and also inhibits the release of excitatory amino acids like glutamate. **3. High-Yield Clinical Pearls for NEET-PG:** * **Vigabatrin Side Effect:** The most characteristic and high-yield adverse effect is **permanent bilateral concentric visual field contraction (tunnel vision)**. Periodic perimetry is mandatory. * **Drug of Choice:** Vigabatrin is a first-line agent for **Infantile Spasms** (West Syndrome), especially when associated with Tuberous Sclerosis. * **Sodium Channel Blockers Mnemonic:** Remember **"PLC"** (Phenytoin, Lamotrigine, Carbamazepine) and **Valproate** (which has multiple mechanisms) as the primary sodium channel inhibitors. * **Contraindication:** Sodium channel blockers (like Phenytoin and Carbamazepine) can worsen **Absence Seizures** and **Myoclonic Seizures**.

Q: Which of the following is NOT a serotonin-norepinephrine reuptake inhibitor?

Tianeptin. **Explanation:** The question asks to identify the drug that does **not** belong to the Serotonin-Norepinephrine Reuptake Inhibitor (SNRI) class. **1. Why Tianeptine is the Correct Answer:** Tianeptine is a unique antidepressant that is chemically classified as a **Selective Serotonin Reuptake Enhancer (SSRE)**. Unlike SSRIs or SNRIs, it paradoxically increases the presynaptic uptake of serotonin, thereby decreasing serotonin levels in the synaptic cleft. It also modulates glutamate neurotransmission and has neuroprotective effects. It is primarily used for Major Depressive Disorder but does not inhibit the reuptake of norepinephrine or serotonin. **2. Why the Other Options are Incorrect:** * **Venlafaxine (A):** The first SNRI introduced. At low doses, it primarily inhibits serotonin reuptake; at higher doses, it significantly inhibits norepinephrine reuptake. * **Duloxetine (B):** A potent SNRI used widely for depression, diabetic neuropathy, fibromyalgia, and stress urinary incontinence. * **Milnacipran (C):** An SNRI with a more balanced inhibition of both serotonin and norepinephrine reuptake compared to venlafaxine. It is frequently used in the management of fibromyalgia. **3. NEET-PG High-Yield Pearls:** * **SNRIs vs. TCAs:** SNRIs are often preferred over Tricyclic Antidepressants (TCAs) because they lack the potent antihistaminic, alpha-adrenergic blocking, and anticholinergic side effects. * **Desvenlafaxine:** This is the active metabolite of venlafaxine. * **Clinical Use:** SNRIs are first-line for depression associated with chronic pain (e.g., Duloxetine). * **Side Effects:** Hypertension is a notable side effect of SNRIs (especially Venlafaxine) due to increased norepinephrine levels.

Question 1

Dantrolene sodium reduces skeletal muscle tone by:

Accepted Answer

Reducing Ca2+ release from sarcoplasmic reticulum in the muscle fibre

Answer

Reducing acetylcholine release from motor nerve endings

Answer

Suppressing spinal polysynaptic reflexes

Answer

Inhibiting the generation of muscle action potential

Question 2

Buspirone is used as a/an?

Accepted Answer

Anxiolytic

Answer

Sedative

Answer

Muscle relaxant

Answer

Anticonvulsant

Question 3

Which of the following drugs can be used as a transcranial patch for the treatment of parkinsonism?

Accepted Answer

Rotigotine

Answer

Levodopa

Answer

Apomorphine

Answer

Aprantine

Question 4

A 10-year-old boy presents with difficulty in learning at school. He experiences short lapses of awareness with eyelid fluttering every 5–10 minutes. EEG studies reveal brief 3 Hz spike and wave discharges appearing synchronously in all leads. Which of the following drugs would be effective but has the disadvantage that it causes sedation and tolerance?

Accepted Answer

Clonazepam

Answer

Diazepam

Answer

Ethosuximide

Answer

Valproic acid

Question 5

Which of the following is NOT a feature of opioid intake?

Accepted Answer

Dilated pupils

Answer

Feeling of relaxation

Answer

Euphoria

Answer

Analgesia

Question 6

Which of the following adverse effects can occur even after the offending drug has been withdrawn a long time back?

Accepted Answer

Tardive dyskinesia

Answer

Paradoxical tachycardia

Answer

Malignant hyperthermia

Answer

Gynaecomastia

Question 7

Natalizumab is used in the treatment of which condition?

Accepted Answer

Multiple sclerosis

Answer

Breast carcinoma

Answer

Psoriasis

Answer

B cell lymphoma

Question 8

A hospital nurse is taking Imipramine for a phobic anxiety disorder, and her patient is being treated with chlorpromazine for a psychotic disorder. Which of the following adverse effects is likely to occur in both of them?

Accepted Answer

Orthostatic hypotension

Answer

Excessive salivation

Answer

Pupillary constriction

Answer

Seizure

Question 9

Which antiepileptic drug does not act via inhibition of sodium channels?

Accepted Answer

Vigabatrin

Answer

Carbamazepine

Answer

Lamotrigine

Answer

Phenytoin

Question 10

Which of the following is NOT a serotonin-norepinephrine reuptake inhibitor?

Accepted Answer

Tianeptin

Answer

Venlafaxine

Answer

Duloxetine

Answer

Milnacipran

Central Nervous System Pharmacology — MCQs

Central Nervous System Pharmacology — MCQs

On this page

Practice by Chapter

Want unlimited practice?