Urea and monoacylureas – Phenacemide MCQs With Answer

Urea and monoacylureas – Phenacemide MCQs With Answer

Urea derivatives and monoacylureas are important chemical classes in medicinal chemistry, with phenacemide historically used as an anticonvulsant representative of monoacylureas. This introduction reviews core concepts B. Pharm students must know: structural features of urea and monoacylureas, basic synthetic routes (acylation of urea), physicochemical properties, structure–activity relationships, pharmacology and likely mechanisms, pharmacokinetics, adverse effects (notably hematologic and hepatic risks), and monitoring requirements. Emphasis is on clinical relevance, toxicities, drug interactions and why safer antiepileptics replaced phenacemide. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What defines a monoacylurea chemically?

• A urea molecule with one hydrogen substituted by an acyl group
• A urea where both nitrogens are acylated
• A cyclic derivative of urea with three acyl groups
• A urea substituted with an alkyl chain only

Correct Answer: A urea molecule with one hydrogen substituted by an acyl group

Q2. Phenacemide is best classified as which type of compound?

• A barbiturate derivative
• A monoacylurea anticonvulsant
• A benzodiazepine
• A succinimide

Correct Answer: A monoacylurea anticonvulsant

Q3. The simplest laboratory route to synthesize monoacylureas typically involves:

• Acylation of urea with an acid chloride or anhydride
• Nitration of urea followed by reduction
• Direct alkylation of urea with alkyl halides
• Condensation of urea with a ketone

Correct Answer: Acylation of urea with an acid chloride or anhydride

Q4. Which functional group is central to both ureas and monoacylureas?

• Carbonyl attached to two nitrogens (–CONH–)
• Ester group (–COOR)
• Thiol group (–SH)
• Nitro group (–NO2)

Correct Answer: Carbonyl attached to two nitrogens (–CONH–)

Q5. Phenacemide’s anticonvulsant action is best described as:

• Precisely known as a GABA-A receptor agonist
• Not fully understood; believed to raise seizure threshold via CNS depression
• A selective sodium channel blocker identical to phenytoin
• A dopamine receptor antagonist

Correct Answer: Not fully understood; believed to raise seizure threshold via CNS depression

Q6. Which adverse effect is historically most associated with phenacemide use?

• Severe blood dyscrasias and hepatic toxicity
• Chronic renal failure as the most common toxicity
• Primary pulmonary fibrosis
• Ototoxicity leading to hearing loss

Correct Answer: Severe blood dyscrasias and hepatic toxicity

Q7. Monitoring required for a patient on phenacemide would typically include:

• Complete blood count and liver function tests
• Routine audiometry and pulmonary function tests
• Urine culture weekly
• Serum amylase and lipase only

Correct Answer: Complete blood count and liver function tests

Q8. Why was phenacemide largely replaced by newer anticonvulsants?

• Because it had limited oral absorption only
• Due to serious adverse effects and better safety profiles of alternatives
• Because it lacked any anticonvulsant efficacy
• Because it was too expensive to manufacture

Correct Answer: Due to serious adverse effects and better safety profiles of alternatives

Q9. Which property of monoacylureas affects their ability to cross the blood–brain barrier?

• Lipophilicity and molecular size
• Presence of a bromine atom only
• Color of the compound
• Number of oxygen atoms exclusively

Correct Answer: Lipophilicity and molecular size

Q10. In structure–activity relationship (SAR) studies, increasing lipophilicity often results in:

• Decreased CNS penetration
• Increased potency due to better brain access
• Complete loss of activity
• Conversion to an antibiotic

Correct Answer: Increased potency due to better brain access

Q11. What is a key difference between urea and monoacylurea?

• Urea has no carbonyl group; monoacylurea does
• Urea has two N–H groups; monoacylurea has one N–H replaced by an acyl group
• Monoacylurea always forms a ring; urea never does
• Urea is aromatic while monoacylurea is aliphatic

Correct Answer: Urea has two N–H groups; monoacylurea has one N–H replaced by an acyl group

Q12. Phenacemide’s administration requires caution with which co-administered substance due to additive CNS depression?

• Alcohol
• Vitamin C
• Calcium carbonate
• Topical ointments

Correct Answer: Alcohol

Q13. Which of the following is a likely pharmacokinetic characteristic of phenacemide?

• Extensive hepatic metabolism
• Excretion unchanged exclusively in urine within minutes
• Not absorbed from the GI tract
• Eliminated through exhalation as a gas

Correct Answer: Extensive hepatic metabolism

Q14. In medicinal chemistry, acylation of urea typically introduces which new bond?

• Amide bond (–CONH–)
• Ether bond (–O–)
• Thioester bond (–COS–)
• Disulfide bond (–S–S–)

Correct Answer: Amide bond (–CONH–)

Q15. Which laboratory parameter best detects early bone marrow suppression from drugs like phenacemide?

• Complete blood count (CBC) with differential
• Serum creatinine only
• Chest X‑ray
• Fasting blood glucose

Correct Answer: Complete blood count (CBC) with differential

Q16. Which statement about phenacemide’s therapeutic indications is correct?

• It was used to treat various forms of epilepsy but is now rarely used
• It is the first-line therapy for acute bacterial meningitis
• It is primarily used as an antidepressant
• It is exclusively a topical antiseptic

Correct Answer: It was used to treat various forms of epilepsy but is now rarely used

Q17. Which structural change to a monoacylurea would most likely increase water solubility?

• Introduction of polar or ionizable groups
• Adding long hydrophobic alkyl chains
• Replacing polar groups with halogens
• Increasing aromatic ring count without polar substituents

Correct Answer: Introduction of polar or ionizable groups

Q18. A critical teaching point about phenacemide in B. Pharm curricula is:

• Understanding historical drug safety lessons and monitoring needs
• That it cures epilepsy permanently after single dose
• It has no known side effects so monitoring is unnecessary
• It is used primarily for pain management now

Correct Answer: Understanding historical drug safety lessons and monitoring needs

Q19. Which chemical property influences a drug’s protein binding and distribution?

• Lipophilicity and affinity for plasma proteins
• Color of the drug solution
• Melting point only
• Number of chlorine atoms exclusively

Correct Answer: Lipophilicity and affinity for plasma proteins

Q20. Which adverse endocrine or metabolic effect is most commonly linked with older anticonvulsants in general?

• Altered hepatic enzyme activity affecting steroid metabolism
• Immediate hyperkalemia in all patients
• Permanent thyroid gland removal
• Causing type 1 diabetes in children

Correct Answer: Altered hepatic enzyme activity affecting steroid metabolism

Q21. Which patient population requires special caution when prescribing agents like phenacemide?

• Patients with pre-existing liver disease or bone marrow disorders
• Healthy young adults with no history of disease
• Those with controlled hypertension only
• Individuals with seasonal allergies only

Correct Answer: Patients with pre-existing liver disease or bone marrow disorders

Q22. Which experimental method helps identify metabolic pathways of monoacylureas?

• In vitro liver microsome studies
• Measuring blood pressure in healthy volunteers
• Infrared spectroscopy of intact tissues only
• Counting white blood cells under a microscope without assays

Correct Answer: In vitro liver microsome studies

Q23. Which clinical sign would prompt immediate discontinuation of phenacemide?

• Sudden signs of bone marrow suppression such as unexplained fever and sore throat
• Mild transient headache once at therapy start
• Temporary dry mouth for a day
• Improvement in seizure control

Correct Answer: Sudden signs of bone marrow suppression such as unexplained fever and sore throat

Q24. Which metabolic reaction commonly modifies monoacylureas in the liver?

• Oxidative metabolism by cytochrome P450 enzymes
• Direct polymerization without enzymes
• Photolysis in the stomach lumen
• Crystallization to inactive salts only

Correct Answer: Oxidative metabolism by cytochrome P450 enzymes

Q25. Which drug interaction concern is most relevant with older anticonvulsants like phenacemide?

• Potential to affect levels of other drugs metabolized by the liver
• Interaction only with topical skin creams
• Only interactions with inhaled gases
• No interactions are ever expected

Correct Answer: Potential to affect levels of other drugs metabolized by the liver

Q26. Which laboratory result would most directly indicate hepatic toxicity?

• Elevated alanine aminotransferase (ALT) and aspartate aminotransferase (AST)
• Low serum sodium only
• High hemoglobin A1c
• Increased urine ketones only

Correct Answer: Elevated alanine aminotransferase (ALT) and aspartate aminotransferase (AST)

Q27. When teaching drug design, monoacylureas are a good example to illustrate:

• How small modifications to urea can alter CNS activity and toxicity
• That only natural products can be CNS active
• That perfume chemistry is unrelated to pharmacology
• That all urea derivatives are antibiotics

Correct Answer: How small modifications to urea can alter CNS activity and toxicity

Q28. Which formulation consideration is relevant for oral monoacylureas?

• Solubility enhancement may be required for adequate absorption
• They can only be given as intravenous emulsions
• They must be refrigerated to remain active
• They are effective only as topical gels

Correct Answer: Solubility enhancement may be required for adequate absorption

Q29. A pharmacology exam question: phenacemide’s onset of anticonvulsant action is generally:

• Dependent on absorption and distribution; not immediate
• Instantaneous upon ingestion
• Only evident after one year of therapy
• Only visible under ultraviolet light

Correct Answer: Dependent on absorption and distribution; not immediate

Q30. Which safety principle is important when a drug has a narrow therapeutic index?

• Careful dosing, monitoring plasma levels if available, and clinical surveillance
• Doubling the dose for faster effect routinely
• Stopping monitoring after first week
• Assuming safety in all age groups equally

Correct Answer: Careful dosing, monitoring plasma levels if available, and clinical surveillance

Q31. Which structural feature often decreases metabolic stability and increases clearance?

• Introduction of polar, readily metabolized functional groups
• Addition of bulky, lipophilic substituents
• Converting to aromatic heterocycles exclusively
• Removing all heteroatoms

Correct Answer: Introduction of polar, readily metabolized functional groups

Q32. Teaching point: Why are historical drugs like phenacemide still studied?

• They provide lessons in SAR, safety, regulatory decisions and clinical monitoring
• They are the cheapest options for all patients today
• They never inform modern drug design
• They are used as dietary supplements

Correct Answer: They provide lessons in SAR, safety, regulatory decisions and clinical monitoring

Q33. Which adverse neurological effect can occur with many CNS depressant anticonvulsants?

• Dizziness and ataxia
• Increased hair growth exclusively
• Instant memory improvement
• Permanent increase in IQ

Correct Answer: Dizziness and ataxia

Q34. For laboratory research on monoacylureas, which technique helps characterize molecular structure?

• NMR spectroscopy
• Basic urine dipstick only
• Counting colonies on agar plates
• Clinical blood pressure measurement

Correct Answer: NMR spectroscopy

Q35. Which regulatory outcome often follows drugs with rare but severe toxicities?

• Restricted use, market withdrawal, or strict monitoring requirements
• Removal of all warnings and unrestricted use
• Mandated use in children only
• Promotion as over‑the‑counter laxatives

Correct Answer: Restricted use, market withdrawal, or strict monitoring requirements

Q36. Which adverse hematological event is most concerning with phenacemide?

• Agranulocytosis or aplastic anemia
• Isolated bruising without lab abnormalities
• Benign red skin spots that are cosmetic only
• Increased red blood cell count always

Correct Answer: Agranulocytosis or aplastic anemia

Q37. Which pharmacodynamic concept is relevant when combining anticonvulsants and other CNS depressants?

• Additive or synergistic CNS depression increasing risk of sedation
• Guaranteed antagonism leading to seizure worsening always
• Complete pharmacological independence with no interactions
• Automatic reversal of toxicity

Correct Answer: Additive or synergistic CNS depression increasing risk of sedation

Q38. Which clinical monitoring schedule is prudent when initiating a drug with hematologic risk?

• Baseline CBC and periodic repeats during therapy
• No baseline tests and only annual checks
• Only urinary pH checks weekly
• Only monitoring body temperature monthly

Correct Answer: Baseline CBC and periodic repeats during therapy

Q39. Compared to newer antiepileptics, phenacemide’s use is limited because it:

• Has greater toxicity and less favorable safety margin
• Is universally more effective than newer agents
• Is tasteless and therefore less accepted
• Only works for headaches

Correct Answer: Has greater toxicity and less favorable safety margin

Q40. In preformulation studies, which characteristic of monoacylureas is typically evaluated?

• Solubility, stability, and permeability
• Ability to turn metal green
• Magnetic properties in a vacuum
• Sound emission on dissolution

Correct Answer: Solubility, stability, and permeability

Q41. Which toxicological test is most relevant to assess mutagenic potential during drug development?

• Ames test
• Urine glucose dipstick
• Baseline chest X‑ray
• Hearing audiogram

Correct Answer: Ames test

Q42. Which feature of monoacylureas can be modified to improve selectivity and reduce toxicity?

• Substituents on aromatic rings and acyl moiety
• The color of the drug bottle
• Only the manufacturer name on the label
• Standard room temperature during storage only

Correct Answer: Substituents on aromatic rings and acyl moiety

Q43. When counseling patients prescribed an older anticonvulsant, which advice is essential?

• Report signs of infection, unusual bruising, jaundice, or severe fatigue immediately
• Stop the drug intermittently without consultation
• Double the dose if a seizure occurs once
• Avoid all fruits during therapy

Correct Answer: Report signs of infection, unusual bruising, jaundice, or severe fatigue immediately

Q44. Which synthetic modification tends to prolong duration of action of CNS drugs?

• Increasing metabolic stability by adding steric hindrance near metabolized sites
• Removing all aromatic rings
• Adding labile ester groups prone to rapid hydrolysis
• Making the molecule highly polar and rapidly excreted

Correct Answer: Increasing metabolic stability by adding steric hindrance near metabolized sites

Q45. In a case of suspected phenacemide-induced hepatotoxicity, the immediate step is:

• Discontinue the drug and perform liver function evaluation
• Increase the dose to overcome toxicity
• Ignore symptoms for 6 months
• Change to topical therapy

Correct Answer: Discontinue the drug and perform liver function evaluation

Q46. Which regulatory documentation typically provides safety updates and monitoring guidance for older drugs?

• Drug labels, safety bulletins and pharmacovigilance reports
• Random social media posts without references
• Commercial advertisements only
• Patient testimonials exclusively

Correct Answer: Drug labels, safety bulletins and pharmacovigilance reports

Q47. For B. Pharm students, a key takeaway about monoacylureas is:

• They illustrate how small chemical changes can markedly affect efficacy and safety
• They are irrelevant to modern pharmacology
• They always guarantee cure of chronic disease
• They function identically to vitamins

Correct Answer: They illustrate how small chemical changes can markedly affect efficacy and safety

Q48. Which type of chemical interaction helps monoacylureas bind targets in the CNS?

• Hydrogen bonding and hydrophobic interactions
• Only ionic bonds with chloride ions
• Permanent covalent bonding to DNA exclusively
• Magnetic attraction to neuronal membranes

Correct Answer: Hydrogen bonding and hydrophobic interactions

Q49. Which experimental model is commonly used to screen anticonvulsant activity in preclinical studies?

• Maximal electroshock seizure (MES) and pentylenetetrazol (PTZ) models
• Human clinical trials only at first step
• Measuring skin thickness in rabbits
• Observing plant growth under drug solution

Correct Answer: Maximal electroshock seizure (MES) and pentylenetetrazol (PTZ) models

Q50. Which phrase best summarizes phenacemide’s legacy in pharmacy education?

• A historical example highlighting drug design, efficacy vs. toxicity trade‑offs and the importance of monitoring
• A current first‑line therapy for all seizure types
• An outdated drug with no learning value
• A medication primarily used for weight loss

Correct Answer: A historical example highlighting drug design, efficacy vs. toxicity trade‑offs and the importance of monitoring

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