Central Nervous System Pharmacology Practice Questions

Q: Which local anesthetic is known for its vasoconstrictive properties?

Cocaine. ***Cocaine*** - Cocaine is unique among local anesthetics for its inherent **sympathomimetic** properties, leading to **vasoconstriction**. - This vasoconstriction is due to its ability to block the reuptake of **norepinephrine** and other catecholamines at adrenergic nerve terminals. *Procaine* - Procaine is an **ester-type** local anesthetic that typically causes **vasodilation**, which can lead to rapid systemic absorption and a shorter duration of action. - It does not possess any inherent vasoconstrictive properties. *Lidocaine* - Lidocaine, an **amide-type** local anesthetic, generally causes **vasodilation** at clinical concentrations. - Due to this vasodilatory effect, **epinephrine** is often added to lidocaine preparations to prolong its action and reduce systemic absorption. *Chlorprocaine* - Chlorprocaine is another **ester-type** local anesthetic known for its rapid onset and short duration of action. - It primarily causes **vasodilation**, similar to procaine, and has no intrinsic vasoconstrictive effects.

Q: What is a key difference between fosphenytoin and phenytoin?

Can be mixed with saline. **Can be mixed with saline** - **Fosphenytoin** is a water-soluble prodrug that is converted to phenytoin in the body; its solubility allows it to be **mixed with saline** solutions for intravenous administration, minimizing the risk of precipitation. - Unlike phenytoin, fosphenytoin's formulation avoids the need for propylene glycol, which is associated with adverse cardiovascular effects and makes phenytoin incompatible with saline. *Can be used in absence seizures* - Neither **fosphenytoin nor phenytoin** is effective for treating **absence seizures**, and they can sometimes worsen them. - **Ethosuximide** or **valproic acid** are the drugs of choice for absence seizures. *Can be given orally* - While **phenytoin** is commonly available in oral forms (capsules, chewable tablets, suspension), **fosphenytoin** is primarily designed for **parenteral administration** (intravenous or intramuscular). - Fosphenytoin is a prodrug that is rapidly converted to phenytoin *in vivo*, but it is not typically available or indicated for direct oral administration. *It is the drug of choice for myoclonic seizures* - Neither **fosphenytoin nor phenytoin** is the drug of choice for **myoclonic seizures**; they can exacerbate this type of seizure. - **Valproic acid** and **levetiracetam** are preferred treatments for myoclonic seizures due to their broader spectrum of activity.

Q: Which of the following antiepileptic drugs is most classically associated with causing hirsutism?

Phenytoin. ***Phenytoin*** - **Phenytoin** is the **most classically associated** antiepileptic drug with **hirsutism**, which is abnormal/excessive growth of hair [1]. - The mechanism involves changes in **androgen metabolism** and stimulation of hair follicle growth. - Other cosmetic side effects include **gingival hyperplasia** and **coarsening of facial features** [1].*Valproate* - Valproate can paradoxically cause both **hair loss (alopecia)** and **hirsutism**, particularly in women and children. - However, phenytoin has a **stronger and more classical association** with hirsutism. - Valproate is also known for **weight gain**, **hepatotoxicity**, **pancreatitis**, and **teratogenicity**.*Carbamazepine* - Carbamazepine's common side effects include **drowsiness**, **dizziness**, **diplopia**, and **hyponatremia**. - It is not classically linked to **hirsutism** as a prominent adverse effect. - Can cause **agranulocytosis** and **Stevens-Johnson syndrome** in rare cases.*Phenobarbitone* - Phenobarbitone is an older antiepileptic drug associated with **sedation**, **cognitive impairment**, and **dependence**. - It does not commonly cause **hirsutism**. - Also causes **enzyme induction** leading to multiple drug interactions.

Q: What is the primary therapeutic use of 5-HT1B/1D agonists?

Acute migraine treatment. ***Acute migraine treatment*** - 5-HT1B/1D agonists, such as **triptans**, primarily work by causing **vasoconstriction of intracranial blood vessels** and inhibiting the release of pro-inflammatory neuropeptides. - This action directly alleviates the pain and associated symptoms of **acute migraine attacks**. *Anti-anxiety medications* - Anti-anxiety medications typically target neurotransmitter systems like **GABA** (e.g., benzodiazepines) or **serotonin reuptake** (e.g., SSRIs), not the 5-HT1B/1D receptors in this context. - While serotonin plays a role in anxiety, specific 5-HT1B/1D agonism does not lead to anxiolytic effects. *Anti-nausea medications for chemotherapy* - Anti-nausea medications used for chemotherapy-induced nausea and vomiting often target **5-HT3 receptors** (e.g., ondansetron) to block their pro-emetic effects. - 5-HT1B/1D agonists do not have primary anti-emetic properties useful in this setting. *Drugs for gastroesophageal reflux disease (GERD)* - GERD medications primarily focus on reducing stomach acid production (e.g., **proton pump inhibitors**, H2 blockers) or neutralizing it (antacids). - 5-HT1B/1D agonists do not directly influence gastric acid secretion or esophageal motility in a way beneficial for GERD.

Q: Which of the following is not a peripherally acting muscle relaxant?

Chlorzoxazone. ***Chlorzoxazone*** - **Chlorzoxazone** is a **centrally acting muscle relaxant** that works by inhibiting polysynaptic reflex arcs in the central nervous system, rather than acting directly on the neuromuscular junction. - Its primary site of action is the **spinal cord** and **subcortical areas** of the brain, leading to generalized muscle relaxation. *Mivacurium* - **Mivacurium** is a **short-acting, non-depolarizing neuromuscular blocker** that acts peripherally by competing with acetylcholine for binding sites on nicotinic receptors at the motor end plate. - It causes muscle relaxation by preventing acetylcholine from depolarizing the muscle fiber, thus inhibiting muscle contraction. *Atracurium* - **Atracurium** is an **intermediate-acting, non-depolarizing neuromuscular blocker** that also acts peripherally at the neuromuscular junction. - It binds to **nicotinic acetylcholine receptors** on the motor end plate, blocking the action of acetylcholine and preventing muscle contraction. *Dantrolene* - **Dantrolene** is a **peripherally acting muscle relaxant** that directly interferes with muscle contraction by inhibiting calcium release from the sarcoplasmic reticulum. - Its unique mechanism of action is directly on the **skeletal muscle fiber**, making it effective in conditions like malignant hyperthermia.

Q: Anandamide is a natural ligand for which of the following receptors?

Cannabinoid receptors. ***Cannabinoid receptors*** - **Anandamide** (N-arachidonoylethanolamine) is an **endocannabinoid**, which means it is an endogenous ligand for the **cannabinoid receptors (CB1 and CB2)** in the body. - Its discovery was crucial in understanding the **endocannabinoid system**, which plays a role in pain modulation, mood regulation, appetite, memory, and neuroprotection. - CB1 receptors are predominantly found in the CNS, while CB2 receptors are more abundant in peripheral tissues and immune cells. *Opioid receptors* - Opioid receptors bind **endogenous opioids** (like endorphins, enkephalins, and dynorphins) and **exogenous opioids** (like morphine), mediating analgesia and other effects. - Anandamide does not bind to opioid receptors; its mechanism of action is distinct and involves the cannabinoid system. *GABA receptors* - **GABA receptors (GABA-A and GABA-B)** are the primary inhibitory neurotransmitter receptors in the CNS, mediating the effects of gamma-aminobutyric acid. - While both the GABAergic and endocannabinoid systems can modulate neuronal excitability, anandamide does not directly bind to GABA receptors. *Dopamine D2 receptors* - **Dopamine D2 receptors** are part of the dopaminergic system, primarily mediating the effects of the neurotransmitter **dopamine** on motor control, reward pathways, and cognition. - While the endocannabinoid and dopaminergic systems can interact functionally, anandamide itself does not directly bind to dopamine D2 receptors.

Q: Which of the following is granted orphan drug status for the treatment of Dravet's syndrome?

Stiripentol. ***Stiripentol*** - **Stiripentol** is an anti-epileptic drug that has been granted **orphan drug status** for its use in treating **Dravet syndrome**. - It is used as an adjunctive therapy, often with clobazam and valproate, to reduce the frequency and severity of seizures in patients with this severe form of epilepsy. *Icatibant* - **Icatibant** is a bradykinin B2 receptor antagonist primarily used for the treatment of acute attacks of **hereditary angioedema (HAE)**. - It is not indicated for epilepsy or Dravet syndrome. *Pitolisant* - **Pitolisant** is a selective histamine H3 receptor antagonist/inverse agonist used to treat **narcolepsy with or without cataplexy**. - Its mechanism of action involves increasing histamine release in the brain to promote wakefulness, which is unrelated to seizure management in Dravet syndrome. *Tafamidis* - **Tafamidis** is a transthyretin stabilizer indicated for the treatment of **transthyretin amyloidosis (ATTR)**, a rare genetic or age-related disease affecting the heart and nerves. - It does not have any approved use or orphan drug status for the treatment of Dravet syndrome.

Q: Which antipsychotic drug is approved for the management of psychosis in Parkinsonian patients?

clozapine. ***Correct: Clozapine*** - **Clozapine** is the only antipsychotic extensively studied and approved for the treatment of **psychosis in Parkinson's disease (PDP)** due to its low propensity to exacerbate motor symptoms. - Its unique pharmacological profile, including lower **D2 receptor blockade** compared to other antipsychotics, makes it suitable for this vulnerable population. - Clozapine has the strongest evidence base for efficacy without worsening motor function in PDP. *Incorrect: Olanzapine* - **Olanzapine** has a significant **risk of worsening motor symptoms** in Parkinson's patients due to its potent **D2 receptor antagonism**. - It is generally contraindicated for treating psychosis in Parkinson's disease. *Incorrect: Haloperidol* - **Haloperidol** is a high-potency typical antipsychotic with strong **D2 receptor blockade**, which can severely **worsen Parkinsonian motor symptoms** (e.g., rigidity, bradykinesia). - Its use is strictly avoided in patients with Parkinson's disease. *Incorrect: Risperidone* - **Risperidone** also carries a considerable risk of **exacerbating motor symptoms** in Parkinson's disease due to its **D2 receptor antagonism**, although less severe than haloperidol. - It is generally not recommended as a first-line treatment for PDP.

Q: What is the maximum dose of plain lignocaine (in mg) for adults?

300. ***300 mg*** - The maximum recommended dose of **plain lidocaine** (without epinephrine) for adults is typically **300 mg** or 4.5 mg/kg, whichever is less. - Exceeding this dose can increase the risk of **systemic toxicity**, including central nervous system and cardiovascular effects. *500 mg* - This dose is generally considered the maximum for **lidocaine with epinephrine** in adults, as **epinephrine** causes vasoconstriction and delays systemic absorption of lidocaine. - For **plain lidocaine**, 500 mg would be an overdose and significantly increase the risk of toxicity. *700 mg* - This is well above the recommended maximum dose for both plain lidocaine and lidocaine with epinephrine, posing a **severe risk of toxicity**. - Such a high dose could lead to **seizures**, cardiac arrhythmias, and even **cardiac arrest**. *1000 mg* - This dose is extremely dangerous and far exceeds any recommended maximum for lidocaine, regardless of whether it contains epinephrine. - Administration of 1000 mg of lidocaine would almost certainly result in **severe and potentially fatal toxicity**.

Question 1

Which local anesthetic is known for its vasoconstrictive properties?

Accepted Answer

Cocaine

Answer

Lidocaine

Answer

Chlorprocaine

Answer

Procaine

Question 2

What is a key difference between fosphenytoin and phenytoin?

Accepted Answer

Can be mixed with saline

Answer

Can be used in absence seizures

Answer

Can be given orally

Answer

It is the drug of choice for myoclonic seizures

Question 3

Which of the following antiepileptic drugs is most classically associated with causing hirsutism?

Accepted Answer

Phenytoin

Answer

Valproate

Answer

Carbamazepine

Answer

Phenobarbitone

Question 4

What is the primary therapeutic use of 5-HT1B/1D agonists?

Accepted Answer

Acute migraine treatment

Answer

Anti-anxiety medications

Answer

Anti-nausea medications for chemotherapy

Answer

Drugs for gastroesophageal reflux disease (GERD)

Question 5

Which of the following is not a peripherally acting muscle relaxant?

Accepted Answer

Chlorzoxazone

Answer

Mivacurium

Answer

Atracurium

Answer

Dantrolene

Question 6

Anandamide is a natural ligand for which of the following receptors?

Accepted Answer

Cannabinoid receptors

Answer

Opioid receptors

Answer

Dopamine D2 receptors

Answer

GABA receptors

Question 7

Which of the following is granted orphan drug status for the treatment of Dravet's syndrome?

Accepted Answer

Stiripentol

Answer

Icatibant

Answer

Pitolisant

Answer

Tafamidis

Question 8

Which antipsychotic drug is approved for the management of psychosis in Parkinsonian patients?

Accepted Answer

clozapine

Answer

risperidone

Answer

olanzapine

Answer

haloperidol

Question 9

What is the maximum dose of plain lignocaine (in mg) for adults?

Accepted Answer

300

Answer

500

Answer

700

Answer

1000

Question 10

All of the following are effects of thiopental, except which of the following?

Accepted Answer

Thiopental is highly lipid soluble, leading to rapid redistribution

Answer

Reduces the cerebral metabolic rate

Answer

Produces dose dependent decrease in blood pressure

Answer

Causes decrease in minute ventilation and tidal volume

Central Nervous System Pharmacology — MCQs

Central Nervous System Pharmacology — MCQs

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