Central Nervous System Pharmacology Practice Questions

Q: In treatment of Parkinsonism, L-Dopa is combined with carbidopa mainly to:

To decrease side effects of L–Dopa. ***To decrease side effects of L–Dopa*** - This is the **primary/main reason** for combining carbidopa with L-Dopa. - Carbidopa is a **peripheral DOPA decarboxylase inhibitor**, preventing the conversion of L-Dopa to dopamine in the periphery. - This reduces side effects like **nausea, vomiting, and cardiac arrhythmias**, which are caused by peripheral dopamine. - Without carbidopa, peripheral side effects make L-Dopa therapy **intolerable at therapeutic doses**. *To decrease dose requirement of L–Dopa* - This is an **important secondary benefit** but not the main reason. - Carbidopa does allow for **75-80% reduction in L-Dopa dose** (from ~5-6g to ~1g daily) by preventing peripheral metabolism. - However, this dose reduction is a **consequence** of preventing peripheral conversion, not the primary therapeutic goal. - The main goal is making L-Dopa therapy **tolerable and safe**, with dose reduction being a beneficial side effect. *To decrease effectiveness of L–Dopa* - Carbidopa **increases the effectiveness** of L-Dopa by ensuring more of it reaches the central nervous system to be converted into dopamine. - By preventing premature peripheral metabolism, carbidopa allows for a greater therapeutic effect on Parkinson's symptoms. *To increase crossing of L–Dopa through BBB* - Carbidopa itself **does not cross the blood-brain barrier (BBB)** and therefore does not directly affect the transport of L-Dopa into the brain. - L-Dopa uses an **active transport system** (large neutral amino acid transporter) to cross the BBB, and carbidopa's role is to prevent its peripheral breakdown before it can utilize this system. - While more L-Dopa reaches the BBB due to reduced peripheral metabolism, carbidopa does not enhance the actual crossing mechanism.

Q: The longest-acting local anaesthetic drug is?

Bupivacaine. ***Bupivacaine*** - **Bupivacaine** is an amide-type local anesthetic known for its **longest duration of action** among commonly used local anesthetics, making it suitable for procedures requiring prolonged anesthesia or pain relief. - Its **high lipid solubility** and **high protein binding** (95%) contribute to its extended effect of **3-10 hours**, allowing a slow release from the tissue. - Duration of action: **180-600 minutes** depending on site and use of vasoconstrictors. *Procaine* - **Procaine** is an ester-type local anesthetic and is one of the **shortest-acting** agents (30-60 minutes) due to its rapid metabolism by plasma pseudocholinesterase. - It is rarely used clinically today due to its short duration and higher incidence of allergic reactions. *Prilocaine* - **Prilocaine** is an amide-type local anesthetic with an **intermediate duration of action** (60-120 minutes), longer than procaine but shorter than bupivacaine. - A potential side effect is the formation of **methemoglobinemia** at higher doses due to its metabolite o-toluidine. *Lignocaine* - Also known as **lidocaine**, it is an amide-type local anesthetic with an **intermediate duration of action**, typically lasting **60-120 minutes**. - It is one of the most commonly used local anesthetics and is also used as an **antiarrhythmic drug** (Class Ib).

Q: Which drug selectively acts on GABA-A receptors to induce sleep with minimal effects on sleep architecture?

Zolpidem. ***Zolpidem*** - **Zolpidem** is a non-benzodiazepine hypnotic that selectively binds to the **omega-1 subtype of GABA-A receptors**, primarily mediating sedation. - This selective action results in sleep induction with **minimal disruption of normal sleep architecture**, making it preferable for insomnia. *Phenobarbitone* - **Phenobarbitone** is a barbiturate that non-selectively enhances GABA-A receptor activity, leading to global CNS depression. - It significantly **disturbs sleep architecture**, reducing REM sleep and slow-wave sleep, and carries a higher risk of dependence and overdose. *Buspirone* - **Buspirone** is an anxiolytic that acts as a partial agonist at **5-HT1A serotonin receptors** and has no direct activity at GABA-A receptors. - It treats generalized anxiety disorder but does **not induce sleep** and is not used as a hypnotic. *Diazepam* - **Diazepam** is a benzodiazepine that non-selectively binds to various subunits of the GABA-A receptor, enhancing GABAergic transmission. - While it induces sleep, it also **significantly alters sleep architecture** (reducing REM and slow-wave sleep) and has a longer half-life, increasing the risk of daytime sedation.

Q: Which of the following synthetic opioids is known for its rapid onset, short duration of action due to high lipid solubility, but does not have local anesthetic effects?

Fentanyl. ***Fentanyl*** - **Fentanyl** is a potent **synthetic opioid** known for its **rapid onset and short duration of action**, primarily due to its **high lipid solubility**. - It works by agonizing μ-opioid receptors but **lacks local anesthetic properties**, unlike some other opioids with structural similarities to local anesthetics. - Its high lipophilicity allows rapid penetration of the blood-brain barrier, contributing to its quick onset of action. *Tramadol* - **Tramadol** is an atypical synthetic opioid that acts as a weak μ-opioid receptor agonist and also inhibits the reuptake of norepinephrine and serotonin. - It exhibits **some local anesthetic-like properties** due to its interaction with neuronal sodium channels, which contributes to its analgesic effect. *Meperidine* - **Meperidine** has a chemical structure similar to local anesthetics and possesses significant **local anesthetic properties**, in addition to its μ-opioid receptor agonist activity. - Its mechanism involves blocking fast sodium channels, which can contribute to local anesthesia, particularly at high concentrations. *Morphine* - **Morphine** is a **naturally-derived opioid** (not synthetic) that primarily acts as a potent agonist at μ-opioid receptors. - While it does not possess significant local anesthetic properties, it differs from fentanyl in being a natural opioid alkaloid with different pharmacokinetic properties (slower onset, longer duration, lower lipid solubility).

Q: Which of the following is not an amide local anesthetic?

Cocaine. ***Cocaine*** - **Cocaine** is an **ester-type** local anesthetic, not an amide. Ester local anesthetics are characterized by an **ester bond** in their chemical structure. - It works by blocking nerve impulse transmission and also by **inhibiting norepinephrine reuptake**, contributing to its vasoconstrictive and stimulatory effects. *Lignocaine* - **Lignocaine** (also known as **lidocaine**) is an **amide-type** local anesthetic, characterized by an **amide bond** in its chemical structure. - Amide local anesthetics are generally more stable and have a longer duration of action compared to ester types. *Prilocaine* - **Prilocaine** is an **amide-type** local anesthetic, commonly used in dentistry and for regional anesthesia. - Its amide structure contributes to its stability and intermediate duration of action. *Bupivacaine* - **Bupivacaine** is an **amide-type** local anesthetic known for its relatively long duration of action and potency. - It is often used for epidural anesthesia and nerve blocks due to its prolonged effect.

Q: Which of the following treatment options for nicotine dependence is considered the least effective?

Nicotine gums. **Nicotine gums** - Among nicotine replacement therapies, **nicotine gums** often show **lower real-world effectiveness** due to adherence challenges and technique requirements. - They require a **specific chewing technique** (chew-and-park method) which is frequently done incorrectly, reducing nicotine absorption and efficacy. - **Adherence rates** are typically lower compared to patches due to taste issues, jaw discomfort, and the need for frequent dosing throughout the day. - Real-world quit rates with gum tend to be **lower than patches** despite similar pharmacological potential when used correctly. *Nicotine patches* - **Nicotine patches** provide **steady-state nicotine delivery** over 16-24 hours with once-daily application. - They have **superior adherence** compared to other NRTs due to convenience and ease of use. - Consistently demonstrate **higher real-world quit rates** among NRTs, making them a first-line option. *Varenicline* - **Varenicline** is a **partial agonist at α4β2 nicotinic receptors**, reducing cravings while blocking rewarding effects of smoking. - It is the **most effective pharmacological treatment** for smoking cessation (quit rates 30-35% vs 15-20% for NRTs). - Superior efficacy compared to all NRTs in multiple meta-analyses and clinical trials. *Nicotine tablets* - **Nicotine lozenges/tablets** dissolve slowly in the mouth, providing **rapid nicotine absorption** through oral mucosa. - They offer **better discretion and convenience** than gum without the chewing technique requirement. - **Adherence and efficacy** are generally comparable to or slightly better than nicotine gum in clinical studies.

Q: Anti-vertigo drug which modulates calcium channels and has a prominent labyrinthine suppressant property is:

Cinnarizine. ***Cinnarizine*** - It is a **selective peripheral vestibular suppressant** that works by inhibiting calcium influx into the vestibular sensory cells. - Its **calcium channel blocking** properties help to reduce the excitability of vestibular organs, thereby alleviating vertigo symptoms. *Cyproheptadine* - This is a **first-generation antihistamine** with anticholinergic and antiserotonergic properties, primarily used for allergy and appetite stimulation. - It does not primarily act as a calcium channel modulator or have significant direct labyrinthine suppressant effects for vertigo. *Clemastine* - This is another **first-generation antihistamine** with anticholinergic effects, primarily used for allergic reactions [1]. - Its main action is blocking histamine H1 receptors, and it lacks the specific calcium channel modulating and vestibular suppressant properties relevant for vertigo treatment. *Cetirizine* - This is a **second-generation antihistamine** that selectively blocks H1 receptors and has minimal sedative effects [2]. - While it can be used for allergic conditions, it does not possess the calcium channel blocking or potent labyrinthine suppressant action required for effective vertigo management.

Q: What are the therapeutic levels of phenytoin?

10-20 mg/ml. ***10-20 mg/ml*** - This range is generally considered the **therapeutic concentration** for phenytoin in most adult patients to achieve adequate seizure control. - Concentrations below this level may be **subtherapeutic**, leading to poor seizure control, while levels above can cause significant **toxicity**. *0-9 mg/ml* - This range is typically **subtherapeutic**, meaning it is too low to effectively control seizures in most patients. - Patients within this range may experience breakthrough seizures, indicating a need to **increase the dose** of phenytoin. *20-29 mg/ml* - This range is considered **toxic** for phenytoin, leading to various dose-related side effects. - Clinical manifestations of toxicity at these levels can include **nystagmus**, ataxia, and slurred speech. *30-39 mg/ml* - This range represents significantly **toxic levels** of phenytoin, associated with severe adverse effects. - At these concentrations, patients can experience pronounced **ataxia**, confusion, lethargy, and potentially even seizure exacerbation.

Q: Which of the following anesthetics is known for its rapid redistribution from the central nervous system to peripheral tissues?

Thiopentone. ***Thiopentone*** - This **barbiturate** is highly **lipid-soluble**, allowing for rapid passage across the **blood-brain barrier**, leading to quick onset of action [2]. - Its short duration of action is primarily due to **rapid redistribution** from the brain to less well-perfused peripheral tissues, not by quick metabolism [1], [3]. - Classic example of an **ultra-short acting intravenous anesthetic** where redistribution is the primary mechanism terminating drug effect [4]. *Propofol* - **Propofol** also undergoes redistribution, but its clinical duration is significantly influenced by **rapid hepatic metabolism** and **high clearance**. - While redistribution contributes to offset, thiopentone is the **classic textbook example** specifically emphasized for redistribution as the primary mechanism [3]. *Halothane* - **Halothane** is an **inhalational anesthetic** whose effects are terminated by elimination via exhalation, not primarily by redistribution. - While some redistribution occurs with all anesthetics, it's not the dominant mechanism for offset of inhalational agents. *Ether* - **Diethyl ether** is an **inhalational anesthetic** with a slow onset and offset due to its high blood-gas solubility and prolonged elimination via the lungs. - Its clinical use has largely been superseded by newer agents due to issues like flammability and slower recovery.

Q: Fenfluramine was historically used for which condition before its withdrawal from the market?

Obesity. ***Obesity*** - Fenfluramine was notably used as an **anorectic agent** (appetite suppressant) for the treatment of **obesity** - Often prescribed in combination with phentermine, known as **"fen-phen"** - The drug was effective in promoting **weight loss** through its mechanism as a **serotonergic agent** that enhanced satiety - It was **withdrawn from the market in 1997** due to associations with **valvular heart disease** and **pulmonary hypertension**, not due to lack of efficacy *Malignancy* - Fenfluramine has **never been approved** or used for the treatment of **malignancy** or cancer - There is no historical or clinical data supporting its use as an anticancer agent - Its mechanism of action is related to appetite suppression, not cancer treatment *Hypertension* - Fenfluramine was **not used to treat hypertension** - Ironically, it was associated with **causing pulmonary hypertension** as a serious adverse effect - Its mechanism as a serotonergic agent for appetite suppression is unrelated to systemic blood pressure control *Diabetes mellitus* - Fenfluramine was not indicated for **diabetes mellitus** treatment - While weight loss can improve glycemic control, fenfluramine was specifically marketed as an **anti-obesity medication**, not an antidiabetic drug

Question 1

In treatment of Parkinsonism, L-Dopa is combined with carbidopa mainly to:

Accepted Answer

To decrease side effects of L–Dopa

Answer

To decrease dose requirement of L–Dopa

Answer

To decrease effectiveness of L–Dopa

Answer

To increase crossing of L–Dopa through BBB

Question 2

The longest-acting local anaesthetic drug is?

Accepted Answer

Bupivacaine

Answer

Procaine

Answer

Prilocaine

Answer

Lignocaine

Question 3

Which drug selectively acts on GABA-A receptors to induce sleep with minimal effects on sleep architecture?

Accepted Answer

Zolpidem

Answer

Phenobarbitone

Answer

Buspirone

Answer

Diazepam

Question 4

Which of the following synthetic opioids is known for its rapid onset, short duration of action due to high lipid solubility, but does not have local anesthetic effects?

Accepted Answer

Fentanyl

Answer

Meperidine

Answer

Tramadol

Answer

Morphine

Question 5

Which of the following is not an amide local anesthetic?

Accepted Answer

Cocaine

Answer

Prilocaine

Answer

Bupivacaine

Answer

Lignocaine

Question 6

Which of the following treatment options for nicotine dependence is considered the least effective?

Accepted Answer

Nicotine gums

Answer

Nicotine tablets

Answer

Nicotine patches

Answer

Varenicline

Question 7

Anti-vertigo drug which modulates calcium channels and has a prominent labyrinthine suppressant property is:

Accepted Answer

Cinnarizine

Answer

Cyproheptadine

Answer

Clemastine

Answer

Cetirizine

Question 8

What are the therapeutic levels of phenytoin?

Accepted Answer

10-20 mg/ml

Answer

0-9 mg/ml

Answer

20-29 mg/ml

Answer

30-39 mg/ml

Question 9

Which of the following anesthetics is known for its rapid redistribution from the central nervous system to peripheral tissues?

Accepted Answer

Thiopentone

Answer

Halothane

Answer

Ether

Answer

Propofol

Question 10

Fenfluramine was historically used for which condition before its withdrawal from the market?

Accepted Answer

Obesity

Answer

Malignancy

Answer

Diabetes mellitus

Answer

Hypertension

Central Nervous System Pharmacology — MCQs

Central Nervous System Pharmacology — MCQs

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