Central Nervous System Pharmacology Practice Questions

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: 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in promoting **weight loss** through its mechanism as a **serotonergic agent** that enhanced satiety - It was **withdrawn from the market in 1997** due to associations with **valvular heart disease** and **pulmonary hypertension**, not due to lack of efficacy *Malignancy* -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

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: Antiviral drug amantadine is approved for treating which of the following conditions?

Parkinsonism. ***Parkinsonism*** - **Amantadine** is an **antiviral agent** that also has **anti-Parkinsonian effects**, particularly useful for treating **dyskinesias** associated with long-term levodopa therapy. - It acts by influencing **dopaminergic neurotransmission** and has **NMDA receptor antagonist** properties. *Schizophrenia* - Schizophrenia is primarily treated with **antipsychotic medications** that target **dopamine** and **serotonin receptors**. - **Amantadine** is not indicated for the treatment of psychosis or other symptoms of schizophrenia. *Depression* - Depression is typically managed with **antidepressants** that modulate **serotonin**, **norepinephrine**, or **dopamine** levels. - **Amantadine** does not have established efficacy as an antidepressant drug. *Alzheimer's disease* - Treatment for Alzheimer's disease often involves **cholinesterase inhibitors** and **NMDA receptor antagonists** like memantine for cognitive symptoms. - While amantadine is an NMDA receptor antagonist, it is **not approved** or commonly used for the primary treatment of Alzheimer's disease.

Q: The following symptoms may be seen in opium withdrawal:

Lacrimation. ***Lacrimation*** - Opioid withdrawal is characterized by **autonomic hyperactivity**, leading to symptoms like **lacrimation** (tearing), rhinorrhea (runny nose), and piloerection. - This is a rebound effect from the chronic opioid suppression of the parasympathetic nervous system. *Tremors* - While tremors can occur in various withdrawal syndromes, they are more characteristic of **alcohol** or **benzodiazepine withdrawal**, which involve GABAergic systems. - Opioid withdrawal can cause muscle aches and spasms, but **significant, sustained tremors** are not a primary diagnostic criterion. *Dry nose and mouth* - **Dry mouth** is a common side effect of opioid use, due to their anticholinergic effects, but during **withdrawal**, patients experience increased secretions like rhinorrhea and **lacrimation**. - **Dry nose** is also contrary to the typical presentation of opioid withdrawal, which involves a **runny nose**. *Constipation* - **Constipation** is a well-known side effect of chronic opioid use due to reduced gut motility. - During withdrawal, patients typically experience **diarrhea** and abdominal cramping, as gut motility returns and often becomes hyperactive.

Q: Which of the following drugs is not effective in the treatment of trigeminal neuralgia?

Acetaminophen. ***Acetaminophen*** - **Acetaminophen** is a common **analgesic** and antipyretic but lacks the direct effect on neuronal hyperexcitability required for treating **neuropathic pain** conditions like trigeminal neuralgia. - Its mechanism of action primarily involves inhibiting prostaglandin synthesis peripherally and centrally, which is insufficient for managing the sharp, stabbing pain of **trigeminal neuralgia**. *Carbamazepine* - **Carbamazepine** is considered the **first-line treatment** for trigeminal neuralgia due to its efficacy in stabilizing hyperexcitable nerve membranes. - It works by blocking **voltage-gated sodium channels**, thereby reducing the firing of trigeminal nerve fibers. *Phenytoin sodium* - **Phenytoin** is an **antiepileptic drug** that can be used as a second-line or adjunctive treatment for trigeminal neuralgia. - Similar to carbamazepine, it acts by **inhibiting voltage-gated sodium channels**, thereby preventing repetitive firing of action potentials. *Baclofen* - **Baclofen** is a **GABA-B receptor agonist** that can be used in combination with carbamazepine or as an alternative for patients who do not respond to or tolerate carbamazepine. - It helps reduce the intensity and frequency of pain by **inhibiting excitatory neurotransmitter release** in the brainstem trigeminal nucleus.

Q: Which of the following statements is FALSE regarding drugs in the treatment of Parkinsonism?

Amantadine is more effective than levodopa. ***Amantadine is more effective than levodopa*** - This statement is **false** because **levodopa** is considered the **gold standard** and most effective treatment for symptomatic Parkinsonism, especially for bradykinesia and rigidity [1, 2]. - While amantadine can be helpful for dyskinesias and offers modest symptomatic relief, its efficacy is significantly **less than levodopa** [1]. *Amantadine causes ankle edema* - This statement is **true**. **Amantadine** is known to cause **peripheral edema**, particularly in the ankles and feet, as a common side effect [1]. - This adverse effect can be managed by reducing the dose or discontinuing the drug if bothersome. *Levodopa is effective in reducing tremors* - This statement is **true**, though with an important caveat. **Levodopa** does reduce tremor in Parkinson's disease, but it is **less effective for tremor** compared to its dramatic effects on bradykinesia and rigidity [1]. - Among parkinsonian symptoms, **tremor responds least well to levodopa** and may require additional agents like anticholinergics or propranolol for optimal control. - Nevertheless, levodopa does provide tremor reduction in most patients, making this statement true overall. *Anti-muscarinic agents are effective in drug-induced Parkinsonism* - This statement is **true**. **Anticholinergic (anti-muscarinic) agents** like benztropine and trihexyphenidyl are often used to treat **drug-induced Parkinsonism**, particularly symptoms like tremor and dystonia [1, 2]. - This form of Parkinsonism is typically caused by dopamine receptor blocking drugs (antipsychotics), making anticholinergics effective by rebalancing cholinergic overactivity.

Q: Which local anesthetic is considered the most cardiotoxic?

Bupivacaine. ***Bupivacaine*** - **Bupivacaine** is an amide-type local anesthetic associated with significant **cardiotoxicity** due to its high lipid solubility and slow dissociation from cardiac sodium channels. - This can lead to severe **arrhythmias** and myocardial depression, making it particularly dangerous in systemic overdose. *Procaine* - **Procaine** is an ester-type local anesthetic with a relatively low potential for cardiotoxicity. - Its rapid metabolism by **plasma pseudocholinesterase** limits systemic exposure and reduces the risk of cardiac effects. *Prilocaine* - **Prilocaine** is an amide-type local anesthetic that is generally less cardiotoxic than bupivacaine. - Its primary concern is the potential to cause **methemoglobinemia** at higher doses, a side effect not directly related to cardiotoxicity. *Ropivacaine* - **Ropivacaine** is an amide-type local anesthetic developed as an alternative to bupivacaine with a reduced cardiotoxicity profile. - It exhibits a more favorable **therapeutic index** for cardiac effects due to its chemical structure and faster dissociation from cardiac sodium channels.

Q: Which of the following drugs is the most commonly prescribed first-line treatment for Alzheimer's disease?

Donepezil. ***Donepezil*** - **Donepezil** is a **centrally acting, reversible acetylcholinesterase inhibitor** and is widely considered the **first-line treatment** for mild to moderate Alzheimer's disease due to its efficacy and once-daily dosing. - It works by increasing the concentration of **acetylcholine** in the synaptic cleft, thereby enhancing cholinergic transmission in the brain. *Rivastigmine* - **Rivastigmine** is also an **acetylcholinesterase inhibitor**, available in oral and transdermal patch formulations, and is used for mild to moderate Alzheimer's. - While effective, it is often considered a **second-line** or alternative agent due to potential for more gastrointestinal side effects compared to donepezil. *Galantamine* - **Galantamine** is another **acetylcholinesterase inhibitor** with an additional mechanism of action as an **allosteric potentiator of nicotinic acetylcholine receptors**. - It is effective in mild to moderate Alzheimer's but is not typically the very first choice given the established prevalence and convenience of donepezil. *Memantine* - **Memantine** is an **NMDA receptor antagonist** and works by blocking the effects of excessive **glutamate**, which is thought to contribute to neurodegeneration in Alzheimer's. - It is generally prescribed for **moderate to severe Alzheimer's disease** and is not considered a first-line treatment for early stages.

Q: Which of the following local anesthetic agents is a vasoconstrictor?

Cocaine. ***Cocaine*** - Cocaine is unique among local anesthetics as it is a potent **vasoconstrictor**, inhibiting **norepinephrine reuptake** at nerve terminals. - This vasoconstrictive property reduces bleeding and prolongs its anesthetic effect, but also contributes to its cardiotoxicity. *Lignocaine* - Lignocaine (Lidocaine) is an **amide-type local anesthetic** that causes **vasodilation**, which can lead to increased systemic absorption and a shorter duration of action [1]. - Due to its vasodilatory effect, **epinephrine** is often added to lignocaine to limit systemic absorption, prolong its effect, and reduce bleeding [1]. *Bupivacaine* - Bupivacaine is a long-acting **amide-type local anesthetic** that typically causes **vasodilation**, similar to lignocaine. - Its high potency and long duration of action make it suitable for local infiltrations and epidural anesthesia, but it also increases the risk of **cardiotoxicity** [1]. *Tetracaine* - Tetracaine is a potent and long-acting **ester-type local anesthetic** that also causes **vasodilation**. - It is primarily used for **spinal anesthesia** and topical applications and is usually combined with vasoconstrictors to prolong its effect.

Question 1

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 2

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

Accepted Answer

Obesity

Answer

Malignancy

Answer

Diabetes mellitus

Answer

Hypertension

Question 3

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 4

Antiviral drug amantadine is approved for treating which of the following conditions?

Accepted Answer

Parkinsonism

Answer

Depression

Answer

Alzheimer's disease

Answer

Schizophrenia

Question 5

The following symptoms may be seen in opium withdrawal:

Accepted Answer

Lacrimation

Answer

Tremors

Answer

Constipation

Answer

Dry nose and mouth

Question 6

Which of the following drugs is not effective in the treatment of trigeminal neuralgia?

Accepted Answer

Acetaminophen

Answer

Phenytoin sodium

Answer

Carbamazepine

Answer

Baclofen

Question 7

Which of the following statements is FALSE regarding drugs in the treatment of Parkinsonism?

Accepted Answer

Amantadine is more effective than levodopa

Answer

Levodopa is effective in reducing tremors

Answer

Amantadine causes ankle edema

Answer

Anti-muscarinic agents are effective in drug-induced Parkinsonism

Question 8

Which local anesthetic is considered the most cardiotoxic?

Accepted Answer

Bupivacaine

Answer

Procaine

Answer

Prilocaine

Answer

Ropivacaine

Question 9

Which of the following drugs is the most commonly prescribed first-line treatment for Alzheimer's disease?

Accepted Answer

Donepezil

Answer

Rivastigmine

Answer

Galantamine

Answer

Memantine

Question 10

Which of the following local anesthetic agents is a vasoconstrictor?

Accepted Answer

Cocaine

Answer

Lignocaine

Answer

Bupivacaine

Answer

Tetracaine

Central Nervous System Pharmacology — MCQs

Central Nervous System Pharmacology — MCQs

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