Central Nervous System Pharmacology Practice Questions

Q: Most cardiotoxic local anesthetic is:

Bupivacaine. ***Bupivacaine*** - **Bupivacaine** is a **highly potent** local anesthetic known for its cardiotoxic effects due to its **lipophilicity** and strong binding to cardiac sodium channels. - Its **slow dissociation** from cardiac sodium channels at toxic plasma concentrations contributes to prolonged arrhythmias and myocardial depression. *Lidocaine* - **Lidocaine** has a **faster onset** and shorter duration of action compared to bupivacaine, making it less cardiotoxic. - While it can cause cardiac effects at high doses, it generally has a **safer cardiac profile** than bupivacaine and is often used as an antiarrhythmic. *Procaine* - **Procaine** is an **ester-type** local anesthetic, which means it is rapidly metabolized by plasma cholinesterases. - This rapid breakdown gives it a **short duration of action** and a **low potential for systemic toxicity**, including cardiotoxicity. *Ropivacaine* - **Ropivacaine** is a **less lipophilic** analog of bupivacaine, designed to have a reduced cardiotoxicity profile. - While it still has potential for cardiotoxicity at very high doses, it demonstrates a **higher therapeutic index** for cardiac rhythm compared to bupivacaine.

Q: What is the classification of Sumatriptan?

5HT 1B/1D agonist. ***5HT 1B/1D agonist*** - Sumatriptan is a **selective serotonin receptor agonist**, specifically targeting the **5-HT1B** and **5-HT1D** receptor subtypes. - This is the **precise pharmacological classification** of triptans used in acute migraine treatment. - Agonism at **5-HT1B receptors** causes **vasoconstriction** of dilated cranial blood vessels. - Agonism at **5-HT1D receptors** inhibits the release of **pro-inflammatory neuropeptides** (CGRP, substance P) from trigeminal nerve endings. - This specific classification distinguishes sumatriptan from non-selective serotonin agonists. *5HT 1 agonist* - While technically not incorrect, this classification is **too broad and imprecise** for pharmacological purposes. - A general "5-HT1 agonist" could theoretically include activity at 5-HT1A, 1B, 1D, 1E, and 1F receptors. - Sumatriptan has **minimal affinity** for 5-HT1A receptors and its therapeutic effect is specifically due to 5-HT1B/1D activity. - In medical literature and standard pharmacology texts, triptans are classified as **5-HT1B/1D agonists**, not general 5-HT1 agonists. *5HT 1D antagonist* - An **antagonist** blocks receptor activity rather than activating it. - This would **worsen** migraine symptoms by preventing the therapeutic effects of endogenous serotonin. - There are no established antimigraine drugs that act as 5-HT1D antagonists. *5HT 1A antagonist* - 5-HT1A receptors are primarily involved in **mood regulation, anxiety, and sleep**, not acute migraine pathophysiology. - Sumatriptan has minimal activity at 5-HT1A receptors. - Antagonism at this receptor would not provide antimigraine effects and is unrelated to sumatriptan's mechanism.

Q: In cases of spasticity, which drug is least likely to be used?

Amitriptyline. ***Amitriptyline*** - **Amitriptyline** is a **tricyclic antidepressant** primarily used for treating depression, neuropathic pain, and migraines. - While it has sedative effects, it does not directly act on the mechanisms that reduce muscle tone in spasticity. *Baclofen* - **Baclofen** is a **GABA-B receptor agonist** that reduces the release of excitatory neurotransmitters, effectively decreasing muscle spasticity. - It is one of the most commonly prescribed drugs for spasticity, available in oral and intrathecal forms. *Tizanidine* - **Tizanidine** is an **alpha-2 adrenergic agonist** that works by increasing presynaptic inhibition of motor neurons, thereby reducing muscle tone. - It is frequently used for spasticity associated with multiple sclerosis or spinal cord injury. *Diazepam* - **Diazepam** is a **benzodiazepine** that acts as a GABA-A receptor agonist, enhancing GABA's inhibitory effects on the central nervous system. - It reduces spasticity by causing generalized muscle relaxation, though its sedative properties can be a limiting side effect.

Q: Which one of the following drugs does not interfere with folic acid metabolism?

Gabapentin. ***Gabapentin*** - **Gabapentin** is an anticonvulsant that primarily exerts its effects by modulating activity at voltage-gated calcium channels; it does **not interfere with folic acid metabolism**. - Its mechanism of action is distinct from other antiepileptic drugs that are known to cause folate deficiency. *Phenobarbitone* - **Phenobarbitone** is an antiepileptic drug that belongs to the barbiturate class and is known to be an **inducer of hepatic microsomal enzymes**. - This enzyme induction can **increase the metabolism of folic acid**, leading to its depletion and potentially megaloblastic anemia. *Primidone* - **Primidone** is an antiepileptic drug that is metabolized to **phenobarbitone** and phenylethylmalonamide (PEMA). - Like phenobarbitone, it is an **hepatic enzyme inducer** and can therefore **interfere with folic acid metabolism**. *Phenytoin* - **Phenytoin** is a well-known antiepileptic drug that often causes **folate deficiency**. - It interferes with folate metabolism by **inhibiting intestinal folate absorption** and by increasing its breakdown through enzyme induction.

Q: The use of levodopa is avoided in which of the following patients?

Psychosis. ***Psychosis*** - Levodopa increases **dopaminergic activity** in the brain, which can significantly worsen or induce **psychotic symptoms** like hallucinations and delusions. - Patients with pre-existing psychosis or a history of psychotic episodes are at high risk, making levodopa a **contraindicated** treatment. *Amyotrophic lateral sclerosis* - **ALS** is a progressive neurodegenerative disease affecting motor neurons, leading to muscle weakness and atrophy. - Levodopa is **not effective** in treating ALS because the disease pathology does not involve dopamine deficiency. *Alzheimer's disease* - While Alzheimer's patients may experience motor symptoms, levodopa is generally not avoided unless there are specific **parkinsonian features** responsive to dopamine. - The primary symptoms of Alzheimer's are **cognitive decline**, which levodopa does not treat and could potentially worsen agitation or confusion in advanced stages. *Essential tremor* - Essential tremor is a movement disorder primarily treated with **beta-blockers** or **anti-seizure medications**. - Levodopa has **no established efficacy** in treating essential tremor, and its use is unrelated to its pathophysiology.

Q: Acute opioid withdrawal is characterized by which of the following symptoms?

Rhinorrhea, Piloerection, Insomnia. ***Rhinorrhea, Piloerection, Insomnia*** - **Rhinorrhea** (runny nose) and **piloerection** (goosebumps) are classic autonomic signs of opioid withdrawal, often described as "cold turkey." - **Insomnia** is a common and distressing symptom of opioid withdrawal, reflecting the hyperactivity of the central nervous system. *Rhinorrhea, Piloerection, Miosis* - While **rhinorrhea** and **piloerection** are characteristic of opioid withdrawal, **miosis** (pupil constriction) is a symptom of **opioid intoxication**, not withdrawal. - Opioid withdrawal typically causes **mydriasis** (pupil dilation) due to sympathetic overactivity. *Rhinorrhea, Piloerection, Constipation* - **Rhinorrhea** and **piloerection** are correct signs of opioid withdrawal. However, **constipation** is a well-known side effect of **opioid use** itself, not a symptom of opioid withdrawal. - Opioid withdrawal more commonly presents with **diarrhea** as gastrointestinal motility increases. *Insomnia, Constipation* - **Insomnia** is a symptom of opioid withdrawal, but **constipation** is not; rather, it is associated with opioid use. - This option also omits other key withdrawal symptoms such as **rhinorrhea** and **piloerection**.

Q: What is the role of marijuana in managing AIDS-related cachexia?

Stimulates appetite. **_Stimulates appetite_** - **Marijuana** (cannabis) and its derivatives, particularly **delta-9-tetrahydrocannabinol (THC)**, are known for their **appetite-stimulating effects** which can combat **cachexia** (wasting syndrome) in AIDS patients [1], [2]. - By increasing appetite, marijuana helps patients consume more calories, thereby reducing **weight loss** and improving overall nutritional status. *Reduces viral load* - There is **no scientific evidence** to suggest that marijuana directly reduces the **viral load** in HIV-infected individuals. - **Antiretroviral therapy (ART)** is the primary and proven method for reducing viral load in AIDS patients. *Enhances CD4 cell count* - Marijuana does **not directly enhance** the **CD4 cell count**, which is a key indicator of immune function in HIV/AIDS. - **Improved nutrition** due to appetite stimulation might indirectly support immune health, but it does not directly increase CD4 cells. *Boosts immune response* - The effect of marijuana on the **immune system** is complex and not fully understood, but it is generally **not considered an immune booster**. - Some studies suggest that cannabinoids may have **immunosuppressive properties**, which would be counterproductive in AIDS [2].

Q: Adverse effects of phenytoin include the following EXCEPT:

Hypercalcemia. ***Hypercalcemia*** - Phenytoin can actually lead to **hypocalcemia** due to its effect on vitamin D metabolism, increasing its degradation and leading to osteomalacia or rickets [1]. - Therefore, **hypercalcemia** is not an expected adverse effect of phenytoin use. *Lymphadenopathy* - **Generalized lymphadenopathy** is a known, though less common, adverse effect of phenytoin, sometimes mimicking lymphoma. - It's part of a broader hypersensitivity reaction that can occur with the drug. *Ataxia* - **Ataxia** is a common dose-dependent adverse effect of phenytoin, especially at higher therapeutic or toxic levels [1], [2]. - It manifests as impaired coordination and balance due to cerebellar dysfunction [1]. *Hirsutism* - **Hirsutism**, or excessive hair growth, is a well-known chronic side effect of phenytoin [1]. - This effect is more aesthetically concerning than medically dangerous and is particularly common in young women [1].

Q: Which of these anticonvulsants causes a contraction of the visual field?

Vigabatrin. ***Vigabatrin*** - **Vigabatrin** is known to cause **irreversible concentric visual field constriction** in a significant percentage of patients, often leading to a permanent reduction in peripheral vision. - This adverse effect, often termed Vigabatrin-associated Visual Field Defect (VAVFD), is due to its impact on the **retina** and is thought to involve GABAergic pathways in the visual system. *Levetiracetam* - **Levetiracetam** is generally well-tolerated and is not commonly associated with significant visual field defects. - Common side effects are primarily neurological, such as **somnolence**, **dizziness**, and **behavioral changes**. *Phenytoin* - **Phenytoin** is more likely to cause dose-related ocular side effects such as **nystagmus** (involuntary eye movements) and **diplopia** (double vision), rather than a contraction of the visual field. - Long-term use can also lead to **gingival hyperplasia** and **hirsutism**. *Ethosuximide* - **Ethosuximide** is primarily used for **absence seizures** and its common side effects are gastrointestinal (**nausea**, **vomiting**, **anorexia**) and neurological (**drowsiness**, **dizziness**, **headache**). - It does not typically cause visual field constriction, which is a rare and specific side effect of certain other anticonvulsants.

Q: Which of the following drugs is not suitable for the management of essential tremors?

Levodopa. ***Levodopa*** - **Levodopa** is primarily used to treat **Parkinson's disease**, specifically targeting its hallmark **bradykinesia** and **rigidity**, not essential tremor. - Its mechanism of action involves increasing dopamine levels in the brain, which is not an effective strategy for essential tremor, and it may even **exacerbate tremor** in some cases. *Diazepam* - **Diazepam**, a **benzodiazepine**, can be used as an adjunct in essential tremor management, particularly for patients experiencing significant **anxiety** that exacerbates their tremor. - It acts by enhancing the effect of **GABA**, leading to a calming effect and muscle relaxation, which can mildly reduce tremor severity. *Metoprolol* - **Metoprolol** is a **beta-blocker** that can be used for essential tremor, especially when **propranolol** is not tolerated or contraindicated. - It works by blocking beta-adrenergic receptors, which helps to reduce the physiological tremor component and is often effective for patients with a triggered or anxiety-related tremor. *Propranolol* - **Propranolol** is considered a **first-line treatment** for essential tremor due to its efficacy in reducing tremor amplitude, particularly in the hands. - It is a non-selective beta-blocker that reduces **sympathetic nervous system** overactivity, which contributes to tremor pathogenesis.

Question 1

Most cardiotoxic local anesthetic is:

Accepted Answer

Bupivacaine

Answer

Procaine

Answer

Lidocaine

Answer

Ropivacaine

Question 2

What is the classification of Sumatriptan?

Accepted Answer

5HT 1B/1D agonist

Answer

5HT 1D antagonist

Answer

5HT 1A antagonist

Answer

5HT 1 agonist

Question 3

In cases of spasticity, which drug is least likely to be used?

Accepted Answer

Amitriptyline

Answer

Baclofen

Answer

Tizanidine

Answer

Diazepam

Question 4

Which one of the following drugs does not interfere with folic acid metabolism?

Accepted Answer

Gabapentin

Answer

Phenobarbitone

Answer

Primidone

Answer

Phenytoin

Question 5

The use of levodopa is avoided in which of the following patients?

Accepted Answer

Psychosis

Answer

Amyotrophic lateral sclerosis

Answer

Alzheimer's disease

Answer

Essential tremor

Question 6

Acute opioid withdrawal is characterized by which of the following symptoms?

Accepted Answer

Rhinorrhea, Piloerection, Insomnia

Answer

Rhinorrhea, Piloerection, Miosis

Answer

Rhinorrhea, Piloerection, Constipation

Answer

Insomnia, Constipation

Question 7

What is the role of marijuana in managing AIDS-related cachexia?

Accepted Answer

Stimulates appetite

Answer

Reduces viral load

Answer

Enhances CD4 cell count

Answer

Boosts immune response

Question 8

Adverse effects of phenytoin include the following EXCEPT:

Accepted Answer

Hypercalcemia

Answer

Ataxia

Answer

Hirsutism

Answer

Lymphadenopathy

Question 9

Which of these anticonvulsants causes a contraction of the visual field?

Accepted Answer

Vigabatrin

Answer

Levetiracetam

Answer

Phenytoin

Answer

Ethosuximide

Question 10

Which of the following drugs is not suitable for the management of essential tremors?

Accepted Answer

Levodopa

Answer

Diazepam

Answer

Propranolol

Answer

Metoprolol

Central Nervous System Pharmacology — MCQs

Central Nervous System Pharmacology — MCQs

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