Paraldehyde MCQs With Answer

Paraldehyde MCQs With Answer is a focused study resource tailored for B. Pharm students preparing for pharmacology and central nervous system (CNS) drug exams. This introduction covers key aspects of paraldehyde: its chemical nature as a cyclic trimer of acetaldehyde, pharmacological actions as a sedative‑hypnotic and anticonvulsant, pharmacokinetics, routes of administration, adverse effects, drug interactions, and quality‑control considerations. The following MCQs emphasize mechanism of action, clinical uses (historical and contemporary), stability, compatibility, analytical methods and safety issues to deepen your understanding. This keyword‑rich guide is optimized for exam preparation, revision and practical pharmacy applications. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the chemical identity of paraldehyde?

• Cyclic trimer of acetaldehyde with formula C6H12O3
• Polymeric ethanol derivative with formula C4H10O2
• Acetal formed from formaldehyde and methanol
• Monomeric aldehyde identical to acetaldehyde

Correct Answer: Cyclic trimer of acetaldehyde with formula C6H12O3

Q2. Which primary pharmacological actions describe paraldehyde?

• Sedative‑hypnotic and anticonvulsant central nervous system depressant
• Direct cholinergic agonist with stimulatory effects
• Selective serotonin reuptake inhibitor
• Peripheral vasodilator with no CNS activity

Correct Answer: Sedative‑hypnotic and anticonvulsant central nervous system depressant

Q3. Which statement correctly describes paraldehyde solubility?

• Miscible with ethanol and many organic solvents; only sparingly soluble in water
• Completely miscible with water in all proportions
• Insoluble in organic solvents but soluble in saline
• Only soluble in strong acids and bases

Correct Answer: Miscible with ethanol and many organic solvents; only sparingly soluble in water

Q4. What is the typical physical description of paraldehyde?

• Colorless oily liquid with a pungent, unpleasant odor
• White crystalline powder with a sweet smell
• Clear gaseous vapor at room temperature
• Blue viscous liquid that is odorless

Correct Answer: Colorless oily liquid with a pungent, unpleasant odor

Q5. How is paraldehyde synthesized industrially?

• By acid‑catalyzed polymerization (trimerization) of acetaldehyde
• By oxidation of ethanol with chromic acid
• By esterification of acetic acid with methanol
• By hydrogenation of acetone

Correct Answer: By acid‑catalyzed polymerization (trimerization) of acetaldehyde

Q6. Which clinical use has historically been associated with paraldehyde?

• Treatment of severe alcohol withdrawal and as an emergency anticonvulsant
• Long‑term management of hypertension
• First‑line therapy for chronic neuropathic pain
• Topical antiseptic for wound care

Correct Answer: Treatment of severe alcohol withdrawal and as an emergency anticonvulsant

Q7. What is the recommended route(s) of administration for paraldehyde in clinical practice?

• Oral and rectal administration are common; intravenous use is not recommended
• Intravenous infusion is the preferred route
• Inhalational aerosol delivery is standard
• Topical application is the primary route

Correct Answer: Oral and rectal administration are common; intravenous use is not recommended

Q8. Which mechanism best explains paraldehyde’s anticonvulsant effect?

• General CNS depression with potentiation of GABAergic inhibitory transmission
• Selective blockade of NMDA glutamate receptors only
• Activation of adrenergic alpha‑1 receptors in the cortex
• Inhibition of peripheral voltage‑gated sodium channels exclusively

Correct Answer: General CNS depression with potentiation of GABAergic inhibitory transmission

Q9. What is a major safety concern when using paraldehyde clinically?

• Risk of severe respiratory depression and aspiration due to vomiting
• High risk of causing profound hypertension
• Marked prolongation of the QT interval in all patients
• Rapid induction of malignant hyperthermia

Correct Answer: Risk of severe respiratory depression and aspiration due to vomiting

Q10. Which interaction is most clinically relevant with paraldehyde?

• Additive central nervous system depression with barbiturates, benzodiazepines and opioids
• It antagonizes the action of all benzodiazepines
• It inactivates antibiotics such as penicillin by direct chemical binding
• It selectively induces CYP2D6 leading to rapid drug clearance

Correct Answer: Additive central nervous system depression with barbiturates, benzodiazepines and opioids

Q11. Which of the following is the correct molecular weight for paraldehyde (C6H12O3)?

• Approximately 132 g/mol
• Approximately 88 g/mol
• Approximately 1500 g/mol
• Approximately 46 g/mol

Correct Answer: Approximately 132 g/mol

Q12. Which analytical technique is commonly used for quantitative assay of paraldehyde in formulations?

• Gas chromatography (GC) due to volatility and organic nature
• Direct titration with sodium hydroxide only
• Nuclear magnetic resonance (NMR) without sample preparation is routine
• Paper chromatography for routine quality control

Correct Answer: Gas chromatography (GC) due to volatility and organic nature

Q13. Paraldehyde is best described chemically as:

• A cyclic acetal (trimer) formed from acetaldehyde molecules
• A linear polymer of ethanol units
• An aldehyde monomer identical to formaldehyde
• A ketone derived from acetone condensation

Correct Answer: A cyclic acetal (trimer) formed from acetaldehyde molecules

Q14. Which storage condition is appropriate for paraldehyde pharmaceutical preparations?

• Keep in tightly closed amber container at room temperature, protected from light
• Store in open containers exposed to air to prevent polymerization
• Must be refrigerated at 2–8°C at all times
• Store in alkaline solutions to maintain stability

Correct Answer: Keep in tightly closed amber container at room temperature, protected from light

Q15. Which adverse effect is commonly associated with paraldehyde use?

• Gastrointestinal irritation with nausea and vomiting
• Severe hyperglycemia in most patients
• Profound diuresis as a consistent effect
• Marked itching and urticaria in the majority

Correct Answer: Gastrointestinal irritation with nausea and vomiting

Q16. Paraldehyde is less commonly used today because:

• Safer and more controllable sedative‑anticonvulsants (benzodiazepines) have replaced it
• It has no sedative properties
• It is too expensive compared with acetaminophen
• It is not effective in any CNS condition

Correct Answer: Safer and more controllable sedative‑anticonvulsants (benzodiazepines) have replaced it

Q17. Which statement about paraldehyde and pregnancy is most appropriate for B. Pharm students?

• Use is generally avoided during pregnancy unless benefit outweighs risk
• It is the preferred agent for insomnia in pregnancy
• It is proven safe and recommended in all trimesters
• Topical application is recommended for teratogenic prophylaxis

Correct Answer: Use is generally avoided during pregnancy unless benefit outweighs risk

Q18. What is an important quality control parameter for paraldehyde liquid preparations?

• Assay of content by gas chromatography and testing for clarity and odor
• Measurement of pH in aqueous solution at 7.5
• Determination of particle size distribution
• Testing for sterility as a topical ophthalmic solution

Correct Answer: Assay of content by gas chromatography and testing for clarity and odor

Q19. Which patient condition represents a relative contraindication to paraldehyde?

• Compromised respiratory function due to risk of respiratory depression
• Mild seasonal allergic rhinitis without systemic involvement
• Controlled hypothyroidism on stable dose of levothyroxine
• Uncomplicated hyperlipidemia well managed with statin therapy

Correct Answer: Compromised respiratory function due to risk of respiratory depression

Q20. How is paraldehyde primarily metabolized in the body?

• Hepatic oxidative metabolism to acetate and further oxidation to CO2
• Excreted unchanged largely via kidneys as the parent compound
• Conjugated by glucuronidation in the plasma and excreted in bile
• Mostly metabolized by gut flora to methane

Correct Answer: Hepatic oxidative metabolism to acetate and further oxidation to CO2

Q21. Which of the following best explains why intravenous administration of paraldehyde is discouraged?

• Risk of severe local and systemic irritation and unpredictable reactions
• It is too highly protein bound for IV delivery
• It causes immediate crystallization in blood
• It is completely inactive if given intravenously

Correct Answer: Risk of severe local and systemic irritation and unpredictable reactions

Q22. What is the principal sensory complaint patients report after receiving paraldehyde?

• Strong, unpleasant taste and odor leading to nausea
• Complete loss of taste and smell permanently
• Increased sweet taste perception
• Persistent metallic taste relieved by citrus

Correct Answer: Strong, unpleasant taste and odor leading to nausea

Q23. Which of the following best describes paraldehyde’s legal and clinical status today?

• Historic drug still available but seldom used; replaced by safer alternatives
• Schedule I controlled substance with no medical use
• Over‑the‑counter remedy for insomnia worldwide
• Banned in all countries for human use

Correct Answer: Historic drug still available but seldom used; replaced by safer alternatives

Q24. In pharmaceutical preparations, paraldehyde is liable to react with strong oxidizing agents. What is the practical implication?

• Store away from oxidizers and avoid contact with nitric acid or peroxides
• It enhances the activity of oxidizing agents and should be mixed to sterilize
• It is stabilized by strong oxidizers and must be formulated with them
• Oxidizing agents have no effect and can be used together safely

Correct Answer: Store away from oxidizers and avoid contact with nitric acid or peroxides

Q25. Which pharmacokinetic property of paraldehyde is most important for emergency use?

• Rapid onset of central nervous system depression after administration
• Extremely long elimination half‑life requiring months for clearance
• Exclusive renal elimination with no hepatic involvement
• Absence of any systemic absorption after oral dosing

Correct Answer: Rapid onset of central nervous system depression after administration

Q26. Which laboratory parameter is most useful when checking formulation identity of paraldehyde?

• Gas chromatographic retention time compared with reference standard
• Serum liver enzymes after one dose
• Visual colorimetric test for sugars
• Measurement of osmolarity in aqueous solution

Correct Answer: Gas chromatographic retention time compared with reference standard

Q27. Paraldehyde’s volatility and smell influence its pharmaceutical handling. Which precaution is appropriate?

• Use in well‑ventilated areas and contain odor with closed containers
• Always heat before opening to increase volatility and reduce odor
• Combine with ammonia to neutralize smell before administration
• No special handling is required as it is odorless

Correct Answer: Use in well‑ventilated areas and contain odor with closed containers

Q28. Which clinical scenario historically justified use of paraldehyde as an emergency measure?

• Status epilepticus when benzodiazepines were unavailable
• Long‑term prophylaxis of migraine headaches
• Routine treatment of chronic insomnia without supervision
• First‑line therapy for acute allergic reactions

Correct Answer: Status epilepticus when benzodiazepines were unavailable

Q29. Which adverse effect should hospital staff anticipate following paraldehyde administration?

• Excessive sedation with potential need for airway support
• Acute hypertensive crisis requiring vasoactive drugs
• Immediate recovery and paradoxical hyperactivity
• Sudden onset of generalized rash in all patients

Correct Answer: Excessive sedation with potential need for airway support

Q30. From a formulation perspective, which excipient compatibility is most important for paraldehyde?

• Avoid strong acids or oxidizers and store with inert packaging
• Always mix with concentrated hydrogen peroxide for stability
• Use with high salt concentrations to enhance solubility
• Exclude all organic solvents to prevent breakdown

Correct Answer: Avoid strong acids or oxidizers and store with inert packaging

Q31. Which monitoring is essential after administering paraldehyde for an acute seizure?

• Continuous monitoring of respiration and oxygenation
• Daily liver enzyme tests for the first 24 hours only
• Routine monitoring of blood glucose every 5 minutes
• No monitoring required due to its benign safety profile

Correct Answer: Continuous monitoring of respiration and oxygenation

Q32. In terms of chemical stability, paraldehyde can revert to acetaldehyde under which conditions?

• In the presence of strong acids or excessive heat leading to depolymerization
• Under basic neutral pH at low temperatures only
• When mixed with sugars in neutral solutions
• After prolonged exposure to ultraviolet light at −20°C

Correct Answer: In the presence of strong acids or excessive heat leading to depolymerization

Q33. Which statement about paraldehyde and hepatic impairment is appropriate?

• Caution is required because hepatic metabolism is an important clearance pathway
• It is excreted unchanged and hepatic function is irrelevant
• Hepatic impairment enhances its safety profile universally
• It cures hepatic encephalopathy and is recommended

Correct Answer: Caution is required because hepatic metabolism is an important clearance pathway

Q34. Which of the following analytical tests would detect degradation of paraldehyde?

• Appearance of acetaldehyde peak on gas chromatogram indicating depolymerization
• Increase in refractive index without any chromatographic change
• Immediate change in pH to neutral in all cases
• Color change to bright green visible at low concentration

Correct Answer: Appearance of acetaldehyde peak on gas chromatogram indicating depolymerization

Q35. What is the approximate boiling point of paraldehyde relevant to handling and GC analysis?

• Approximately 124–126°C
• Approximately 37°C
• Approximately 500°C
• It sublimes at room temperature and has no boiling point

Correct Answer: Approximately 124–126°C

Q36. In pediatric emergency settings historically, why was rectal paraldehyde used?

• As an alternative route when intravenous access was not available and oral intake was unsafe
• Because it is the preferred long‑term antiepileptic in children
• Because it enhances growth and development in neonates
• Due to its strong sweet flavor acceptable to infants

Correct Answer: As an alternative route when intravenous access was not available and oral intake was unsafe

Q37. Which statement about paraldehyde’s odor is clinically relevant during administration?

• The pungent odor can provoke nausea and vomiting, increasing aspiration risk
• The odor is pleasant and aids patient compliance
• It has no odor and therefore no clinical implications
• Odorless formulations are standard in hospitals

Correct Answer: The pungent odor can provoke nausea and vomiting, increasing aspiration risk

Q38. Which storage container material is preferred for paraldehyde?

• Amber glass bottles with tight caps to prevent volatilization and light exposure
• Polycarbonate open containers stored in direct sunlight
• Aluminum cans that react with the liquid to stabilize it
• Porous ceramic jars for slow release of odor

Correct Answer: Amber glass bottles with tight caps to prevent volatilization and light exposure

Q39. From a mechanistic perspective, paraldehyde’s CNS depression is most similar to which class?

• General anesthetics and sedative‑hypnotics that potentiate GABA‑mediated inhibition
• Beta‑blockers that reduce sympathetic tone peripherally only
• Cholinesterase inhibitors that enhance acetylcholine transmission
• MAO inhibitors that increase monoamine levels acutely

Correct Answer: General anesthetics and sedative‑hypnotics that potentiate GABA‑mediated inhibition

Q40. What is a correct statement regarding compatibility of paraldehyde with intravenous fluids?

• It is not compatible with routine intravenous fluids and IV administration is discouraged
• It is fully compatible with all parenteral solutions and safe for continuous infusion
• It requires dilution in concentrated saline to activate its effects
• It can be mixed with blood products without any concern

Correct Answer: It is not compatible with routine intravenous fluids and IV administration is discouraged

Q41. Which precaution should a pharmacist give when dispensing paraldehyde preparations?

• Warn patients about strong odor and advise taking measures to reduce aspiration risk if vomiting occurs
• Advise that it may be safely combined with alcohol at home
• Recommend heating before use to enhance potency
• Inform patients that no special precautions are needed because it is inert

Correct Answer: Warn patients about strong odor and advise taking measures to reduce aspiration risk if vomiting occurs

Q42. Which statement best describes the modern relevance of paraldehyde in pharmacotherapy?

• It remains an important historical anticonvulsant but is rarely used due to safer alternatives
• It is the current first‑line treatment for epilepsy worldwide
• It is primarily used as an antibiotic today
• It is universally preferred for chronic sedation in outpatient settings

Correct Answer: It remains an important historical anticonvulsant but is rarely used due to safer alternatives

Q43. What monitoring should be available when paraldehyde is administered in an acute care setting?

• Cardiorespiratory monitoring including pulse oximetry and readiness for airway management
• Only blood pressure checks once per day
• Serial X‑rays to monitor deposition in the lungs
• No monitoring is required due to rapid metabolism

Correct Answer: Cardiorespiratory monitoring including pulse oximetry and readiness for airway management

Q44. Which of the following best reflects paraldehyde’s effect on the liver enzymes?

• Chronic or high‑dose use may stress hepatic metabolism and requires caution
• It is a potent inducer of all hepatic enzymes and increases clearance of all drugs immediately
• It completely spares the liver and improves hepatic function
• It acts as a competitive inhibitor of ALT and AST assays

Correct Answer: Chronic or high‑dose use may stress hepatic metabolism and requires caution

Q45. Which laboratory sign would suggest accidental ingestion of a degraded paraldehyde product?

• Presence of free acetaldehyde detected by gas chromatography
• Marked hypernatremia on basic metabolic panel
• Elevated urinary ketones only after weeks
• Immediate drop in hemoglobin concentration by half

Correct Answer: Presence of free acetaldehyde detected by gas chromatography

Q46. For exam preparation, which topic is most important when studying paraldehyde for B. Pharm?

• Pharmacology (mechanism), clinical uses, safety, routes, stability and assay methods
• Manufacture of insulin analogues in comparison
• Use in veterinary dermatology as a topical cream
• Comparative economics of vaccine production

Correct Answer: Pharmacology (mechanism), clinical uses, safety, routes, stability and assay methods

Q47. Which patient education point is most appropriate when paraldehyde is dispensed?

• Advise against concomitant alcohol or other sedatives and warn about drowsiness
• Recommend driving and operating heavy machinery immediately after use
• Advise combining with OTC stimulants to counteract drowsiness
• State there are no interactions with prescription CNS drugs

Correct Answer: Advise against concomitant alcohol or other sedatives and warn about drowsiness

Q48. Which factor makes paraldehyde less favorable compared to modern benzodiazepines?

• Unpleasant odor, variable dosing, aspiration risk and narrower safety margin
• It has stronger anxiolytic effects with no sedation
• It is completely non‑sedating and therefore ineffective
• It is cheaper but more effective without side effects

Correct Answer: Unpleasant odor, variable dosing, aspiration risk and narrower safety margin

Q49. Which statement is true regarding paraldehyde’s formulation in pharmacies?

• It requires careful labeling, odor containment and secure storage away from oxidizers
• It is typically dispensed as a powdered tablet for easy dissolution
• It is always formulated as an aqueous injectable solution for convenience
• It must be stored frozen at −80°C to remain stable

Correct Answer: It requires careful labeling, odor containment and secure storage away from oxidizers

Q50. Which summary statement best prepares a B. Pharm student for exam questions on paraldehyde?

• Understand its chemistry (acetaldehyde trimer), CNS depressant pharmacology, historical clinical uses, safety concerns and analytical/stability issues
• Memorize that it is identical to benzodiazepines and acts via the same receptor binding site exclusively
• Focus solely on its use as a topical antiseptic and ignore CNS effects
• Assume it is safe for unsupervised home use in combination with alcohol

Correct Answer: Understand its chemistry (acetaldehyde trimer), CNS depressant pharmacology, historical clinical uses, safety concerns and analytical/stability issues

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