Central Nervous System Pharmacology — MCQs
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Ketamine belongs to which of the following group of drugs ?
Which drug can exhibit Phase II neuromuscular block:
A recently approved drug for treatment of the 'off phenomenon' in Parkinsonism:
Modafinil is approved by FDA for treatment of all except:
Main site of action of tetanus toxin:
Which drug is suitable for epilepsy related to a brain tumor?
Drugs used in ADHD are:
What is the drug of choice for treatment of simple partial seizures?
The treatment of post traumatic epilepsy is -
A patient with grand mal epilepsy would likely be under treatment with:
Central Nervous System Pharmacology Indian Medical PG Practice Questions and MCQs
Question 691: Ketamine belongs to which of the following group of drugs ?
- A. Phenols
- B. Barbiturate
- C. Phencyclidine (Correct Answer)
- D. Benzodiazepine
Explanation: ***Phencyclidine***- **Ketamine** is structurally related to **phencyclidine (PCP)**, sharing a similar mechanism of action as an **NMDA receptor antagonist** [2]. Ketamine is also categorized as a general anesthetic [1].- Both drugs primarily induce a state of **dissociative anesthesia**, characterized by a trance-like state without loss of consciousness [2].*Phenols*- **Phenols** are a class of organic compounds typically used as antiseptics and disinfectants, such as carbolic acid.- They do not possess anesthetic properties or a similar chemical structure to ketamine.*Barbiturate*- **Barbiturates** are central nervous system depressants that produce a wide range of effects, including sedation, hypnosis, and anesthesia [3].- They act primarily by enhancing the activity of **GABA-A receptors**, a different mechanism than ketamine.*Benzodiazepine*- **Benzodiazepines** are a class of psychoactive drugs primarily used for treating anxiety, insomnia, and seizures.- They also act by enhancing **GABA-A receptor** activity, leading to central nervous system depression, unlike ketamine's dissociative effects.
Question 692: Which drug can exhibit Phase II neuromuscular block:
- A. Scoline (Correct Answer)
- B. Cocaine
- C. D-TC
- D. Vencuronium, ether, N2O
Explanation: ***Scoline*** - **Scoline** (**succinylcholine**) is a depolarizing neuromuscular blocker that can cause a **Phase II block** with prolonged or high-dose administration. - In a Phase II block, the neuromuscular junction becomes desensitized to acetylcholine, leading to a block that resembles a **non-depolarizing block**, including fade and post-tetanic potentiation. *Cocaine* - **Cocaine** is a local anesthetic and a stimulant; it primarily acts by blocking the reuptake of **norepinephrine**, **dopamine**, and **serotonin** in the central nervous system. - It does not directly affect the neuromuscular junction to cause a depolarizing or Phase II block. *Vencuronium, ether, N2O* - **Vencuronium** is a **non-depolarizing neuromuscular blocker** that produces a competitive block at the neuromuscular junction, which is distinct from a Phase II block. - **Ether** is an inhaled anesthetic that can cause muscle relaxation but does not typically induce a Phase II neuromuscular block. **N2O** (nitrous oxide) is a weak anesthetic with no significant neuromuscular blocking properties. *D-TC* - **d-tubocurarine (d-TC)** is a **non-depolarizing neuromuscular blocker** that competitively antagonizes acetylcholine at the nicotinic receptors. - Unlike scoline, it does not cause initial depolarization or a subsequent Phase II block.
Question 693: A recently approved drug for treatment of the 'off phenomenon' in Parkinsonism:
- A. Safinamide (Correct Answer)
- B. Ziconotide
- C. Evenamide
- D. Lacosamide
Explanation: ***Safinamide*** - **Safinamide** is a recently approved drug that acts as a **reversible monoamine oxidase B (MAO-B) inhibitor** and also modulates **glutamate release**. - It is specifically indicated as an adjunct therapy for Parkinson's disease patients experiencing motor fluctuations ("off" time) treated with levodopa. *Ziconotide* - **Ziconotide** is a synthetic **conopeptide** that selectively blocks N-type calcium channels. - It is used for the management of severe chronic pain in patients for whom intrathecal therapy is warranted, not for Parkinsonism. *Evenamide* - **Evenamide** is an investigational drug, currently in clinical trials, primarily developed as an adjunctive treatment for **schizophrenia**. - It works as a **glutamate modulator** but is not approved for Parkinson's disease. *Lacosamide* - **Lacosamide** is an anti-epileptic drug that selectively enhances **slow inactivation of voltage-gated sodium channels**. - It is used for the treatment of **partial-onset seizures** and has no indication for Parkinson's disease.
Question 694: Modafinil is approved by FDA for treatment of all except:
- A. Narcolepsy
- B. Shift work sleep disorder (SWSD)
- C. Obstructive sleep apnea syndrome (OSAS)
- D. Lethargy in depression (Correct Answer)
Explanation: ***Lethargy in depression*** - Modafinil is **not FDA-approved** for treating lethargy or fatigue specifically in the context of depression. Its primary indications are for disorders of excessive daytime sleepiness. - While it may be used off-label in some cases for depression-related fatigue, it lacks formal FDA approval and specific efficacy data for this indication. *Narcolepsy* - Modafinil is **FDA-approved** as a wakefulness-promoting agent for the treatment of excessive daytime sleepiness associated with **narcolepsy**. - It helps reduce the frequency and severity of sleep attacks by promoting wakefulness through effects on **dopamine**, **norepinephrine**, and **histamine** systems in the brain. *Shift work sleep disorder (SWSD)* - Modafinil is **FDA-approved** to improve wakefulness in patients with excessive sleepiness associated with **shift work sleep disorder**. - It helps individuals working non-traditional hours (night shifts, rotating shifts) maintain alertness during their work periods. *Obstructive sleep apnea syndrome (OSAS)* - Modafinil is **FDA-approved** as an **adjunctive treatment** for residual excessive daytime sleepiness in patients with **obstructive sleep apnea/hypopnea syndrome (OSAHS)** who are receiving adequate treatment with CPAP. - It addresses persistent sleepiness that remains even after appropriate primary airway management.
Question 695: Main site of action of tetanus toxin:
- A. Neuromuscular junction
- B. Muscle fibers
- C. Postsynaptic terminal of spinal cord
- D. Presynaptic terminal of spinal cord (Correct Answer)
Explanation: ***Presynaptic terminal of spinal cord*** - The **tetanus toxin** (tetanospasmin) travels via **retrograde axonal transport** to the **presynaptic terminals** of inhibitory interneurons in the spinal cord. - It then cleaves **synaptobrevin**, a protein essential for the release of inhibitory neurotransmitters **GABA** and **glycine**, leading to uncontrolled muscle spasms. *Neuromuscular junction* - While it can be transported through the motor neurons supplying the neuromuscular junction, its primary site of action for systemic effects is not directly at the junction itself. - Toxins like **botulinum toxin** primarily act at the neuromuscular junction to inhibit acetylcholine release. *Muscle fibers* - Tetanus toxin does not directly act on muscle fibers to cause contraction or paralysis. - Muscle hyperexcitability is an indirect result of disinhibited motor neurons. *Postsynaptic terminal of spinal cord* - Tetanus toxin does not directly bind to or act on the postsynaptic receptors of the spinal cord neurons. - Its mechanism involves preventing the release of neurotransmitters from the **presynaptic terminal**.
Question 696: Which drug is suitable for epilepsy related to a brain tumor?
- A. Levetiracetam (Correct Answer)
- B. Phenytoin
- C. Phenobarbitone
- D. Carbamazepine
Explanation: ***Levetiracetam*** - Levetiracetam is often preferred for **tumor-related epilepsy** due to its favorable **pharmacokinetic profile**, minimal **drug-drug interactions**, and broad spectrum of activity against various seizure types. - It does not significantly induce or inhibit hepatic enzymes, making it a safer option for patients who may be on other medications for their tumor or cancer treatment. *Phenytoin* - **Phenytoin** has a narrow **therapeutic window** and significant **drug-drug interactions** due to its potent hepatic enzyme induction, which can complicate concomitant use with **chemotherapy** or other medications. - It also has a dose-dependent non-linear pharmacokinetic profile, making dose adjustments challenging and increasing the risk of **toxicity**. *Phenobarbitone* - **Phenobarbitone** is a potent enzyme inducer and has a high potential for **sedation** and cognitive side effects, which can significantly impair the quality of life for patients. - Its long half-life and propensity for **drug interactions** make it less desirable, especially in patients with brain tumors who may experience other neurological deficits. *Carbamazepine* - **Carbamazepine** is another potent **enzyme inducer** that can lead to significant **drug interactions**, particularly with chemotherapy agents, altering their metabolism and efficacy. - It often causes side effects like **drowsiness**, **dizziness**, and can lead to **hyponatremia**, which may be problematic in patients who are already compromised.
Question 697: Drugs used in ADHD are:
- A. Methylphenidate
- B. Dextro-amphetamine
- C. Atomoxetine
- D. All of the options (Correct Answer)
Explanation: ***All of the options*** - **Methylphenidate**, **dextro-amphetamine**, and **atomoxetine** are all commonly used medications for the treatment of **Attention-Deficit/Hyperactivity Disorder (ADHD)** [1]. - These drugs work through different mechanisms to improve symptoms such as inattention, hyperactivity, and impulsivity. *Methylphenidate* - This is a **stimulant medication** that works by increasing the levels of **dopamine** and **norepinephrine** in the brain [2]. - It is one of the most frequently prescribed drugs for ADHD, available in various formulations (short-acting, long-acting) [1]. *Dextro-amphetamine* - This is also a **stimulant medication** that enhances the release of **dopamine** and **norepinephrine**, similar to methylphenidate [1]. - It is another highly effective treatment for ADHD and is available in forms like Adderall (mixed amphetamine salts) and Vyvanse (lisdexamfetamine) [1]. *Atomoxetine* - This is a **non-stimulant medication** that acts as a selective **norepinephrine reuptake inhibitor (SNRI)**. - It is an alternative for individuals who do not respond to stimulants, cannot tolerate them, or have coexisting anxiety disorders; it has a slower onset of action compared to stimulants.
Question 698: What is the drug of choice for treatment of simple partial seizures?
- A. Carbamazepine (Correct Answer)
- B. Phenytoin
- C. Valproate
- D. Barbiturate
Explanation: ***Carbamazepine*** - **Carbamazepine** is the **traditional drug of choice** for **simple partial (focal) seizures** and remains a first-line agent in clinical practice. - It is a **sodium channel blocker** that works by stabilizing the inactivated state of voltage-gated sodium channels, thereby **reducing neuronal excitability** and preventing the spread of epileptic activity. - It has proven **efficacy** and a well-established safety profile, making it a preferred initial monotherapy option. - Note: Newer agents like levetiracetam and lamotrigine are also considered first-line alternatives in modern guidelines. *Phenytoin* - **Phenytoin** is also a **sodium channel blocker** and effective for **partial seizures**, but is typically reserved as a **second-line or alternative agent**. - It has a **less favorable side effect profile** including gingival hyperplasia, hirsutism, and cerebellar atrophy. - Its **narrow therapeutic index** and complex pharmacokinetics (zero-order elimination at therapeutic doses) with multiple drug interactions make carbamazepine generally preferred for initial therapy. *Valproate* - **Valproate** (valproic acid) has a **broad spectrum of activity** and is effective against both partial and generalized seizures. - For **simple partial seizures**, carbamazepine is typically preferred as valproate has more significant adverse effects including **hepatotoxicity**, **pancreatitis**, and **teratogenicity** (especially important in women of childbearing age). - Valproate is often the drug of choice for **generalized seizures** (absence, myoclonic, generalized tonic-clonic). *Barbiturate* - **Barbiturates** (e.g., phenobarbital) are older antiepileptic drugs that enhance **GABAergic inhibition**. - Their use has significantly declined due to high incidence of **sedation**, **cognitive impairment**, and **risk of dependence**. - They are generally considered less desirable as first-line agents compared to newer, better-tolerated drugs like carbamazepine.
Question 699: The treatment of post traumatic epilepsy is -
- A. Long term anticonvulsants (Correct Answer)
- B. Long term corticosteroids
- C. Immediate corticosteroids
- D. Mannitol infusion
Explanation: ***Long term anticonvulsants*** - **Post-traumatic epilepsy** is a chronic condition characterized by recurrent seizures following a head injury. Long-term **anticonvulsant medications** are the primary treatment to prevent these recurrent seizures. - The choice of anticonvulsant depends on the seizure type and patient-specific factors, aiming to achieve seizure control with minimal side effects. *Long term corticosteroids* - **Corticosteroids** are not indicated for the long-term management or prevention of post-traumatic epilepsy. - Their primary use would be in reducing inflammation or edema, which is not the long-term goal of epilepsy treatment. *Immediate corticosteroids* - **Immediate corticosteroids** might be used in acute head injury to reduce cerebral edema, but they do not prevent or treat subsequent **epilepsy**. - They do not address the underlying neuronal hyperexcitability that leads to seizures in post-traumatic epilepsy. *Mannitol infusion* - **Mannitol** is an osmotic diuretic used acutely to reduce **intracranial pressure** in severe head injuries. - It does not have any role in the long-term treatment or prevention of **epilepsy**.
Question 700: A patient with grand mal epilepsy would likely be under treatment with:
- A. Pentobarbital
- B. Trimethadione
- C. Meprobamate
- D. Phenytoin (Correct Answer)
Explanation: ***Phenytoin*** - **Phenytoin** is a classic and effective anticonvulsant widely used for treating **generalized tonic-clonic seizures** (grand mal epilepsy) [2], [4]. - Its mechanism involves blocking voltage-gated sodium channels, stabilizing the neuronal membrane and preventing the repetitive firing of action potentials [3]. *Pentobarbital* - **Pentobarbital** is a barbiturate primarily used as a sedative or for inducing medical coma, especially in refractory status epilepticus. - While it has anticonvulsant properties, it is not a first-line agent for the long-term management of chronic grand mal epilepsy due to its side effect profile and sedative effects. *Trimethadione* - **Trimethadione** is an older anticonvulsant specifically used for **absence seizures** (petit mal epilepsy). - It works by reducing T-type calcium currents in thalamic neurons, a mechanism distinct from that required for generalized tonic-clonic seizures [1]. *Meprobamate* - **Meprobamate** is a carbamate derivative primarily used as an anxiolytic and muscle relaxant. - It has sedative properties but is not considered an effective or appropriate treatment for any type of epilepsy, including grand mal seizures.
Practice by Chapter
General Anesthetics
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Local Anesthetics
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Sedative-Hypnotics
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Antiepileptic Drugs
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Opioid Analgesics
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Drugs of Abuse and Addiction
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Psychostimulants
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Hallucinogens
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CNS Stimulants and Cognitive Enhancers
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