Central Nervous System Pharmacology Practice Questions

Q: A 67-year-old man with Parkinson disease has experienced an increasingly dry mouth for the past 3 months, and this interferes with eating and swallowing. He has noted dry eyes as well. On physical examination, he has minimal tremor at rest; there are no other abnormal findings. Laboratory studies show no detectable autoantibodies. Which of the following is the most likely cause for his findings?

Anticholinergic drug use. ***Anticholinergic drug use***- Many medications used to treat **Parkinson disease** have **anticholinergic effects**, which can lead to **dry mouth (xerostomia)** and **dry eyes (xerophthalmia)** due to reduced glandular secretions [1].- The patient's presentation of worsening dry mouth and dry eyes aligns well with the side effects of such medications.*Alcohol ingestion*- While chronic alcohol use can contribute to **dehydration** and indirectly affect salivary production, it is typically not the primary cause of such pronounced and progressive symptoms in this context, nor does it commonly cause dry eyes.- The patient's symptoms are more consistent with a direct pharmacological effect rather than general dehydration from alcohol.*Candidiasis*- Oral candidiasis usually presents with **white plaques** on the oral mucosa, **soreness**, or difficulty swallowing due to pain, not primarily dry mouth and dry eyes.- The physical examination did not reveal any other abnormal findings, making candidiasis less likely as the primary cause.*Sialadenitis with blockage of salivary duct*- **Sialadenitis** (inflammation of salivary glands) or salivary duct obstruction typically causes **pain**, **swelling**, and localized tenderness in the affected gland, often exacerbated by eating.- This condition generally affects salivation but does not explain the concurrent dry eyes, making it an unlikely sole cause for both symptoms.

Q: What deficiency is commonly associated with the use of Dilantin (phenytoin)?

Folic acid deficiency. ***Folic acid deficiency*** - **Phenytoin** is known to interfere with **folate metabolism** and absorption in the gastrointestinal tract, leading to a deficiency. - This deficiency can result in **megaloblastic anemia** with prolonged use. *Thiamine deficiency* - **Thiamine deficiency** (beriberi) is not typically associated with phenytoin use but rather with alcoholism, malnutrition, or malabsorption. - While certain antiepileptics might cause various nutritional deficiencies, thiamine is not a primary concern with phenytoin. *Nicotinamide deficiency* - **Nicotinamide (niacin) deficiency** causes pellagra and is characterized by dermatitis, diarrhea, and dementia. It is not directly linked to phenytoin. - This deficiency is often seen in individuals with diets poor in niacin, like corn-based diets, or in chronic alcoholism. *Riboflavin deficiency* - **Riboflavin deficiency** (ariboflavinosis) can cause angular stomatitis, cheilosis, and glossitis, but it is not a common side effect of phenytoin. - While various drug interactions can affect nutrient levels, phenytoin's primary known interaction is with folate.

Q: Which of the following drugs is primarily used for the treatment of Parkinson's disease?

Levodopa. ***Levodopa*** - Levodopa is a **dopamine precursor** that crosses the blood-brain barrier and is converted to dopamine in the brain, replacing the depleted dopamine in Parkinson's disease [1], [2]. - It is considered the **most effective drug** for managing the motor symptoms of Parkinson's disease, particularly in the early and moderate stages [2], [4]. *Mazindol* - **Mazindol** is an appetite suppressant used for obesity and acts primarily as a norepinephrine-dopamine reuptake inhibitor. - It is **not indicated** for the treatment of Parkinson's disease. *Benserazide* - **Benserazide** is a **peripheral DOPA decarboxylase inhibitor** that does not cross the blood-brain barrier [1]. - It is used in combination with levodopa (e.g., in co-beneldopa) to prevent the peripheral metabolism of levodopa, increasing its availability to the brain, but it is **not used alone** to treat Parkinson's disease [1]. *Bromocriptine* - **Bromocriptine** is a **dopamine agonist** that directly stimulates dopamine receptors in the brain [3]. - While used in Parkinson's disease, it is generally considered a **second-line treatment** or used as an adjunct to levodopa, and not the primary drug [3].

Q: Which of the following is a non-cholinergic agent?

Memantine. ***Memantine*** - Memantine is an **NMDA receptor antagonist** and works by blocking the effects of excessive **glutamate**, a neurotransmitter that can contribute to neuronal damage in Alzheimer's disease. - Unlike the other options, it does not directly interfere with the **acetylcholine** system but rather modulates glutamatergic neurotransmission. *Galantamine* - Galantamine is an **acetylcholinesterase inhibitor** and an allosteric modulator of nicotinic acetylcholine receptors. - It increases the availability of **acetylcholine** in the synaptic cleft, making it a cholinergic agent. *Donepezil* - Donepezil is a **reversible acetylcholinesterase inhibitor** used in the treatment of Alzheimer's disease. - Its mechanism of action involves increasing the concentration of **acetylcholine** in the brain, thus it is a cholinergic agent. *Tacrine* - Tacrine was one of the first **acetylcholinesterase inhibitors** approved for Alzheimer's disease. - It works by preventing the breakdown of **acetylcholine**, thereby increasing its levels in the brain and is considered a cholinergic agent.

Q: Which of the following drugs is least preferred for the treatment of multiple sclerosis?

Mycophenolate. ***Mycophenolate*** - **Mycophenolate mofetil** is an immunosuppressant typically used to prevent **organ transplant rejection** and in autoimmune diseases like **lupus nephritis**. - While it has immunosuppressive properties, it is **not approved** or considered a first-line or even second-line treatment for **multiple sclerosis (MS)** due to a lack of robust evidence of efficacy and a less favorable risk-benefit profile compared to other established MS therapies. *Interferon beta-1a* - **Interferon beta-1a** is a **disease-modifying therapy (DMT)** widely used for **relapsing-remitting multiple sclerosis (RRMS)**, reducing relapse rates and slowing disease progression. - It works by modulating the **immune response** to decrease inflammation and demyelination in the central nervous system. *Interferon beta-1b* - Similar to interferon beta-1a, **interferon beta-1b** is an established **DMT** for **RRMS** and some forms of **secondary progressive MS**. - It also functions through **immunomodulation**, helping to reduce the frequency and severity of relapses. *Glatiramer acetate* - **Glatiramer acetate** is an **immunomodulator** approved for the treatment of **RRMS**, working by mimicking myelin basic protein and inducing T-cell tolerance. - It effectively **reduces relapse rates** and is considered a safe and well-tolerated option for long-term use in MS patients.

Q: The drug of choice for absence attacks is

Ethosuximide. ***Ethosuximide*** - **Ethosuximide** is the most effective and preferred drug for treating **absence seizures** due to its selective mechanism of action. - It works by blocking **T-type calcium channels** in the thalamus, which are crucial for generating the characteristic 3-Hz spike-and-wave discharges of absence seizures. *Phenytoin* - **Phenytoin** is primarily used for **tonic-clonic seizures** and **focal seizures**, but it is generally ineffective for absence seizures and can even worsen them. - Its mechanism of action involves stabilizing neuronal membranes by **blocking voltage-gated sodium channels**, which is not the primary pathophysiology of absence seizures. *Primidone* - **Primidone** is an anticonvulsant that is metabolized to **phenobarbital** and **phenylethylmalonamide (PEMA)**. It is effective for **generalized tonic-clonic** and **focal seizures**. - It is not considered a first-line treatment for **absence seizures** and may not be effective. *Phenobarbitone* - **Phenobarbitone** (phenobarbital) is a barbiturate effective against **generalized tonic-clonic** and **focal seizures** but is not a drug of choice for absence seizures. - While it has broad-spectrum anticonvulsant activity by enhancing **GABAergic inhibition**, it is less effective and has more prominent sedative side effects compared to ethosuximide for absence epilepsy.

Q: Which one of the following drugs has a narrow therapeutic range?

Phenytoin. ***Phenytoin*** - **Phenytoin** has a **narrow therapeutic index**, meaning there is a small difference between the therapeutic and toxic doses. - This necessitates **therapeutic drug monitoring** to ensure effective treatment while avoiding adverse effects like nystagmus, ataxia, or gingival hyperplasia. *Propranolol* - **Propranolol** is a **beta-blocker** used for hypertension, angina, and arrhythmias, generally considered to have a wide therapeutic range. - While dose adjustments are common, routine therapeutic drug monitoring is typically **not required** due to its relatively safe profile at higher doses compared to drugs like phenytoin. *Piroxicam* - **Piroxicam** is a **nonsteroidal anti-inflammatory drug (NSAID)** with a relatively wide therapeutic window. - Its primary concerns are gastrointestinal and renal side effects rather than toxicity from a narrow therapeutic range. *Prazosin* - **Prazosin** is an **alpha-1 adrenergic blocker** used for hypertension and benign prostatic hyperplasia, and it generally has a wide therapeutic range. - The main concern with prazosin is **first-dose phenomenon** (orthostatic hypotension), which is an initial effect rather than toxicity from a narrow therapeutic window.

Q: Diplopia and ataxia are the adverse effects of which of the following drugs?

Phenytoin and carbamazepine. ***Phenytoin and carbamazepine*** - Both **phenytoin** and **carbamazepine** are well-known to cause **diplopia** (double vision) and **ataxia** (impaired coordination) as dose-related adverse effects, especially at higher therapeutic levels. - These neurological side effects occur due to their impact on the **central nervous system**, affecting motor control and ocular movements. *Gabapentin and carbamazepine* - While **carbamazepine** can cause diplopia and ataxia, **gabapentin** primarily causes dizziness, drowsiness, and fatigue, but less commonly diplopia or significant ataxia at therapeutic doses. - Gabapentin's mechanism of action differs from carbamazepine, leading to a distinct adverse effect profile. *Gabapentin with phenytoin* - **Phenytoin** is associated with diplopia and ataxia, but **gabapentin** is less likely to cause these specific effects compared to phenytoin. - The combination would not be the primary answer for both drugs specifically causing prominent diplopia and ataxia. *Valproate and topiramate* - **Valproate** can cause tremor and sedation but is less commonly associated with prominent diplopia and ataxia. - **Topiramate** frequently causes cognitive slowing, word-finding difficulties, and paresthesias, but diplopia and ataxia are not its most characteristic adverse effects.

Q: Which of the following is FALSE about ropivacaine?

Contains only R enantiomer. ***Contains only R enantiomer*** - Ropivacaine is a **pure S-enantiomer** (S-(-)-enantiomer) preparation, NOT the R-enantiomer. - This single enantiomer formulation contributes to its **reduced cardiotoxicity** and improved safety profile compared to racemic bupivacaine. - The statement "contains only R enantiomer" is **FALSE** - this is the correct answer. *Less cardiotoxic than bupivacaine* - Ropivacaine has **lower lipid solubility** and faster dissociation from cardiac sodium channels compared to bupivacaine. - This results in **significantly reduced cardiotoxicity**, making it safer for large-volume regional blocks. - This statement is **TRUE**. *More cardiotoxic than lignocaine* - Ropivacaine is indeed **more cardiotoxic than lidocaine** due to its greater potency and longer duration of action. - Amide local anesthetics with higher potency (bupivacaine > ropivacaine > lidocaine) carry greater cardiac risk. - This statement is **TRUE**. *Onset of action is faster than bupivacaine* - Ropivacaine and bupivacaine have **similar onset times** (10-15 minutes for epidural/nerve blocks). - Both have similar pKa values (ropivacaine 8.1, bupivacaine 8.1), resulting in comparable onset characteristics. - While ropivacaine may have marginally faster onset in some contexts, clinically they are considered equivalent. - This statement is generally **FALSE or equivocal**, making it potentially the second-best answer, but the R-enantiomer statement is definitively false.

Q: Which ergot-derived dopamine receptor agonist is known to cause cardiac valvular fibrosis?

Pergolide & cabergoline. ***Pergolide & cabergoline*** - Both **Pergolide** and **Cabergoline** are **ergot-derived dopamine agonists** [1], [2], [3] that have been associated with **cardiac valvular fibrosis** [1], [2]. - This adverse effect is mediated by their agonistic activity on **5-HT2B serotonin receptors** located on heart valve fibroblasts [2]. *Levodopa* - **Levodopa** is a precursor to dopamine and is used to treat Parkinson's disease, but it is not an ergot derivative [1]. - It does not directly cause cardiac valvular fibrosis; its main side effects are related to motor complications and gastrointestinal issues. *Ropinrole* - **Ropinrole** is a **non-ergot dopamine agonist** used for Parkinson's disease and restless legs syndrome [1]. - Unlike ergot-derived agonists, it has a lower affinity for 5-HT2B receptors and is not significantly associated with cardiac valvular fibrosis. *Pramipexole* - **Pramipexole** is another **non-ergot dopamine agonist** with a similar safety profile to ropinirole regarding cardiac health [1]. - It does not cause cardiac valvular fibrosis and is generally preferred over ergot derivatives due to their cardiovascular side effects.

Question 1

A 67-year-old man with Parkinson disease has experienced an increasingly dry mouth for the past 3 months, and this interferes with eating and swallowing. He has noted dry eyes as well. On physical examination, he has minimal tremor at rest; there are no other abnormal findings. Laboratory studies show no detectable autoantibodies. Which of the following is the most likely cause for his findings?

Accepted Answer

Anticholinergic drug use

Answer

Alcohol ingestion

Answer

Candidiasis

Answer

Sialadenitis with blockage of salivary duct

Question 2

What deficiency is commonly associated with the use of Dilantin (phenytoin)?

Accepted Answer

Folic acid deficiency

Answer

Thiamine deficiency

Answer

Nicotinamide deficiency

Answer

Riboflavin deficiency

Question 3

Which of the following drugs is primarily used for the treatment of Parkinson's disease?

Accepted Answer

Levodopa

Answer

Mazindol

Answer

Benserazide

Answer

Bromocriptine

Question 4

Which of the following is a non-cholinergic agent?

Accepted Answer

Memantine

Answer

Galantamine

Answer

Donepezil

Answer

Tacrine

Question 5

Which of the following drugs is least preferred for the treatment of multiple sclerosis?

Accepted Answer

Mycophenolate

Answer

Interferon beta-1b

Answer

Interferon beta-1a

Answer

Glatiramer acetate

Question 6

The drug of choice for absence attacks is

Accepted Answer

Ethosuximide

Answer

Phenytoin

Answer

Primidone

Answer

Phenobarbitone

Question 7

Which one of the following drugs has a narrow therapeutic range?

Accepted Answer

Phenytoin

Answer

Propranolol

Answer

Piroxicam

Answer

Prazosin

Question 8

Diplopia and ataxia are the adverse effects of which of the following drugs?

Accepted Answer

Phenytoin and carbamazepine

Answer

Gabapentin and carbamazepine

Answer

Gabapentin with phenytoin

Answer

Valproate and topiramate

Question 9

Which of the following is FALSE about ropivacaine?

Accepted Answer

Contains only R enantiomer

Answer

More cardiotoxic than lignocaine

Answer

Less cardiotoxic than bupivacaine

Answer

Onset of action is faster than bupivacaine

Question 10

Which ergot-derived dopamine receptor agonist is known to cause cardiac valvular fibrosis?

Accepted Answer

Pergolide & cabergoline

Answer

Levodopa

Answer

Ropinrole

Answer

Pramipexole

Central Nervous System Pharmacology — MCQs

Central Nervous System Pharmacology — MCQs

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