Central Nervous System Pharmacology Practice Questions

Q: Which of the following is the most effective oral drug for smoking cessation?

Varenicline. ***Varenicline*** - **Varenicline** is a partial agonist at **α4β2 nicotinic acetylcholine receptors**, reducing the reward from smoking and alleviating withdrawal symptoms. - Clinical trials consistently demonstrate its superior efficacy compared to **bupropion** and **nicotine replacement therapy** in achieving long-term abstinence. - It is the **most effective FDA-approved oral medication** for smoking cessation with quit rates approximately 2-3 times higher than placebo. *Bupropion* - **Bupropion** is an antidepressant that acts as a **norepinephrine-dopamine reuptake inhibitor**, which can reduce cravings and withdrawal symptoms. - While effective, its efficacy is generally considered to be lower than that of **varenicline** for smoking cessation. - It is considered a **first-line alternative** for patients who cannot tolerate varenicline. *Nicotine gum* - **Nicotine gum** is an oral form of nicotine replacement therapy that delivers nicotine without the harmful chemicals of tobacco, helping to manage withdrawal symptoms. - It is effective but less successful than **varenicline** when used as monotherapy, though combination NRT approaches can improve outcomes. - Available in 2 mg and 4 mg strengths, with dosing based on smoking history. *Nortriptyline* - **Nortriptyline** is a tricyclic antidepressant that has shown some efficacy in reducing nicotine withdrawal symptoms, but its use is limited by its side effect profile. - It is considered a **second-line agent** for smoking cessation due to its lower efficacy and greater potential for adverse effects (anticholinergic, cardiac) compared to first-line options like **varenicline** and **bupropion**.

Q: Which of the following is a new drug approved for Rett syndrome?

Trofinetide. ***Trofinetide*** - **Trofinetide**, marketed as Daybue, was approved by the FDA in **March 2023** specifically for the treatment of **Rett syndrome**. - It is a synthetic analog of **glycine-proline-glutamate (GPE)**, which is a cleavage product of **insulin-like growth factor-1 (IGF-1)**, and is thought to reduce neuroinflammation and improve synaptic function. - This is the **first and only FDA-approved drug** specifically indicated for Rett syndrome. *Sodium oxybate* - **Sodium oxybate (Xyrem)** is a CNS depressant (gamma-hydroxybutyrate or GHB) primarily used for the treatment of **narcolepsy with cataplexy**. - It is a GABA-B receptor agonist and has sedative properties, but it is **not approved for Rett syndrome**. - It does not address the underlying pathophysiology or core symptoms of Rett syndrome. *Memantine* - **Memantine** is an NMDA receptor antagonist used primarily for moderate to severe **Alzheimer's disease**. - While it has been studied in some neurodevelopmental disorders, it is **not approved for Rett syndrome**. - It may help with certain symptoms but is not a disease-specific treatment. *Lunesta* - **Lunesta (eszopiclone)** is a nonbenzodiazepine sedative-hypnotic medication used for the treatment of **insomnia**. - It is not indicated for **Rett syndrome** and would only address sleep disturbances symptomatically, not the core neurological deficits.

Q: Which of the following is the most effective drug in smoking cessation?

Varenicline. ***Varenicline*** - **Varenicline** is a **partial agonist** of the **nicotinic acetylcholine receptor (nAChR)**, reducing cravings and withdrawal symptoms while blocking the pleasurable effects of nicotine. - It has been shown to be more effective than other pharmacological interventions, including bupropion and nicotine replacement therapies, in achieving **long-term abstinence**. *Nicotine gum* - **Nicotine gum** is a form of **Nicotine Replacement Therapy (NRT)** that provides nicotine to reduce withdrawal symptoms. - While effective, NRTs (including gum) are generally less effective than varenicline in achieving sustained smoking cessation. *Buspirone* - **Buspirone** is an anxiolytic drug primarily used to treat generalized anxiety disorder. - It does not have a primary indication or significant evidence of effectiveness for smoking cessation. *Rimonabant* - **Rimonabant** is a **cannabinoid receptor 1 (CB1) antagonist** that was once explored for smoking cessation and weight loss. - It was withdrawn from the market due to significant psychiatric side effects, including depression and suicidal ideation, and is not used for smoking cessation.

Q: What is the mechanism of action of local anesthetics?

Block sodium channels. ***Block sodium channels*** - Local anesthetics work by **reversibly binding** to the alpha subunit of **voltage-gated sodium channels** on the neuronal membrane. - This binding prevents the influx of sodium ions, thereby inhibiting the **depolarization** of the neuron and **propagation of action potentials**. *Block chloride channels* - **Chloride channels** are primarily involved in **hyperpolarization** or stabilization of the resting membrane potential, and their blockade is not the primary mechanism of local anesthesia. - Drugs like **benzodiazepines** modulate GABA-gated chloride channels for their anxiolytic and sedative effects. *Block calcium channels* - **Calcium channels** are important for neurotransmitter release and muscle contraction, but their blockade is not the way local anesthetics exert their effects. - **Calcium channel blockers** are used in cardiovascular medicine (e.g., diltiazem, verapamil) to reduce heart rate and blood pressure. *Block potassium channels* - **Potassium channels** are crucial for repolarization of the neuronal membrane and maintaining the resting potential. - While some toxins block potassium channels, it is not the principal mechanism by which **local anesthetics** achieve their nerve blocking effect.

Q: All of the following drugs are used for prophylaxis of migraine except;

Flutamide. ***Flutamide*** - **Flutamide** is an **antiandrogen** used in the treatment of prostate cancer, not for migraine prophylaxis. - Its mechanism of action involves blocking androgen receptors, which is irrelevant to migraine pathophysiology. *Flunarizine* - **Flunarizine** is a **calcium channel blocker** commonly used for migraine prophylaxis due to its vascular effects. - It helps stabilize neuronal membranes and reduce cerebral vasospasm, preventing migraine attacks. *Imipramine* - **Imipramine** is a **tricyclic antidepressant (TCA)** that can be used off-label for migraine prevention due to its neuromodulatory effects. - It works by affecting neurotransmitter levels, particularly serotonin and norepinephrine, which play a role in migraine pathways. *Propranolol* - **Propranolol** is a **beta-blocker** widely used for migraine prophylaxis, especially in patients with coexisting hypertension or anxiety. - Its mechanism involves modulating adrenergic activity and potentially stabilizing cortical excitability.

Q: Least teratogenic antiepileptic drug in pregnancy is:

Levetiracetam. ***Levetiracetam*** - **Levetiracetam** is generally considered one of the **safest antiepileptic drugs (AEDs)** during pregnancy, with a lower risk of major congenital malformations compared to other AEDs. - Studies have shown a **low incidence of neural tube defects** and other severe malformations when used as monotherapy. *Carbamazepine* - **Carbamazepine** is associated with an increased risk of **neural tube defects**, particularly **spina bifida**, during pregnancy. - It can also cause other malformations such as **facial dysmorphism** and developmental delays. *Valproate* - **Valproate** has the **highest teratogenic potential** among common AEDs, linked to a significantly increased risk of **neural tube defects**, **cardiac anomalies**, and **cognitive impairment (fetal valproate syndrome)**. - Due to its high risk, its use is generally **contraindicated in women of childbearing potential** unless no other effective alternative exists. *Phenytoin* - **Phenytoin** is associated with **fetal hydantoin syndrome**, characterized by specific facial features, **growth deficiency**, developmental delay, and increased risk of cleft lip/palate, and **cardiac defects**. - It is known for its **dose-dependent teratogenicity**, making careful monitoring crucial.

Q: All of the following are actions produced by mu receptors of morphine except:-

Hyperalgesia. ***Hyperalgesia*** - **Hyperalgesia** is not a primary physiological action of **μ-opioid receptor** activation; the fundamental role of these receptors is to produce **analgesia** by inhibiting pain transmission. - While **opioid-induced hyperalgesia** can occur with chronic use, it is a paradoxical compensatory response rather than a direct cellular action of the morphine-receptor complex. *Respiratory depression* - Activation of **μ-receptors** in the **brainstem** directly reduces the sensitivity of the respiratory center to **carbon dioxide**, leading to decreased respiratory rate. - This is one of the most clinically significant side effects and is the primary cause of death in **opioid overdose**. *Miosis* - Morphine stimulates the **Edinger-Westphal nucleus** via μ-receptors, resulting in excessive parasympathetic output to the eye. - This produces **pinpoint pupils**, a classic diagnostic sign of **opioid toxicity** that does not develop tolerance. *Decreased GI motility* - **μ-receptors** are highly expressed in the **myenteric plexus** of the gut, where their activation inhibits the release of acetylcholine and slows **peristalsis**. - This action results in **constipation**, which is a universal side effect of morphine therapy and typically requires prophylactic management.

Q: Which of the following anti-epileptic drugs has the highest teratogenic potential?

Valproate. ***Correct: Valproate*** - **Valproate has the highest teratogenic potential** among all anti-epileptic drugs, with a **10-20% risk of major congenital malformations** - **Neural tube defects** (spina bifida) occur in **1-2% of exposed pregnancies**, which is 10-20 times higher than the general population - Other significant risks include **cardiac malformations, craniofacial abnormalities**, and **neurodevelopmental disorders** (autism spectrum disorder, reduced IQ) - **Fetal valproate syndrome** is a recognized clinical entity - Current guidelines strongly recommend **avoiding valproate in women of childbearing potential** unless no alternatives exist *Incorrect: Carbamazepine* - Has teratogenic risks but significantly **lower than valproate** (2-5% risk of major malformations) - Associated with **neural tube defects** (0.5-1% risk, lower than valproate) - Considered a safer alternative when valproate must be avoided *Incorrect: Phenytoin* - Causes **fetal hydantoin syndrome** with characteristic features: craniofacial anomalies, nail/digital hypoplasia, growth restriction, and developmental delay - Teratogenic risk is **moderate** (approximately 5-10% risk of major malformations) - Risk is significant but **lower than valproate** *Incorrect: Lamotrigine* - Considered **one of the safest anti-epileptic drugs** during pregnancy - Low teratogenic risk with **major malformation rate of 2-3%** (close to baseline population risk) - Slight increased risk of **oral clefts** at higher doses - **Preferred choice** for women of childbearing potential requiring anti-epileptic therapy

Q: Shortest acting local anaesthetic

Chloroprocaine. ***Chloroprocaine*** - **Chloroprocaine** is known for its rapid onset and very **short duration of action**, typically lasting 30-60 minutes, due to its **rapid hydrolysis** by plasma and liver esterases. - Its quick metabolism makes it suitable for short procedures where a brief blockade is desired, minimizing the risk of systemic toxicity. *Dibucaine* - **Dibucaine** is a local anesthetic with a **long duration of action**, typically 2 to 4 hours, which is much longer than chloroprocaine. - It is used topically and in spinal anesthesia, but its prolonged effect makes it unsuitable as the shortest-acting option. *Procaine* - **Procaine** is an ester-type local anesthetic with a relatively **short duration of action** (approximately 30-60 minutes), but it is generally longer than that of chloroprocaine. - It was one of the first synthetic local anesthetics and is less potent and shorter-acting than many modern agents. *Cocaine* - **Cocaine** has a moderate duration of action as a local anesthetic, typically lasting 60-90 minutes, which is longer than chloroprocaine. - While it is a potent local anesthetic and vasoconstrictor, its high abuse potential and systemic side effects limit its clinical use, mainly to topical application in otolaryngology.

Question 1

Which of the following is the most effective oral drug for smoking cessation?

Accepted Answer

Varenicline

Answer

Bupropion

Answer

Nortriptyline

Answer

Nicotine gum

Question 2

Which of the following is a new drug approved for Rett syndrome?

Accepted Answer

Trofinetide

Answer

Sodium oxybate

Answer

Memantine

Answer

Lunesta

Question 3

Which of the following is the most effective drug in smoking cessation?

Accepted Answer

Varenicline

Answer

Nicotine gum

Answer

Buspirone

Answer

Rimonabant

Question 4

Which of the following is true regarding nicotine substitution therapy?

Accepted Answer

There should be a 15-minute gap between nicotine gum and coffee/soda/acidic food as they decrease its absorption

Answer

Preferably given by gastrointestinal route.

Answer

Varenicline comes with a black box warning of cardiovascular death

Answer

Nicotine chewing gum is better for constant use as it gives 25% higher blood level than lozenges

Question 5

What is the mechanism of action of local anesthetics?

Accepted Answer

Block sodium channels

Answer

Block chloride channels

Answer

Block calcium channels

Answer

Block potassium channels

Question 6

All of the following drugs are used for prophylaxis of migraine except;

Accepted Answer

Flutamide

Answer

Flunarizine

Answer

Imipramine

Answer

Propranolol

Question 7

Least teratogenic antiepileptic drug in pregnancy is:

Accepted Answer

Levetiracetam

Answer

Carbamazepine

Answer

Valproate

Answer

Phenytoin

Question 8

All of the following are actions produced by mu receptors of morphine except:-

Accepted Answer

Hyperalgesia

Answer

Respiratory depression

Answer

Miosis

Answer

Decreased GI motility

Question 9

Which of the following anti-epileptic drugs has the highest teratogenic potential?

Accepted Answer

Valproate

Answer

Carbamazepine

Answer

Phenytoin

Answer

Lamotrigine

Question 10

Shortest acting local anaesthetic

Accepted Answer

Chloroprocaine

Answer

Dibucaine

Answer

Procaine

Answer

Cocaine

Central Nervous System Pharmacology — MCQs

Central Nervous System Pharmacology — MCQs

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