Barbital MCQs With Answer

Barbital MCQs With Answer is an essential study resource tailored for B.Pharm students preparing for pharmacology, medicinal chemistry, and pharmaceutics exams. This concise, keyword-rich introduction and the following question set cover barbital’s chemistry, synthesis, mechanism of action, pharmacokinetics, formulation, analytical methods, adverse effects, and drug interactions. Each MCQ emphasizes clinical relevance, structure–activity relationships, assay techniques and regulatory considerations to deepen your conceptual understanding. Questions range from basic identification to applied problem-solving, helping you retain facts and reason through therapeutic and toxicological implications. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the chemical name commonly used for barbital?

• Diethylbarbituric acid
• Phenobarbital
• Thiopental sodium
• Secobarbital

Correct Answer: Diethylbarbituric acid

Q2. Barbital primarily acts by modulating which receptor system?

• GABA-A receptor chloride channel
• Nicotinic acetylcholine receptor
• NMDA glutamate receptor
• Serotonin 5-HT3 receptor

Correct Answer: GABA-A receptor chloride channel

Q3. Which structural feature at the C-5 position of barbiturates is most important for sedative-hypnotic activity?

• Alkyl or aryl substitutions
• Hydroxylation at C-3
• Methylation of the ring nitrogen
• Sulfur substitution at C-2

Correct Answer: Alkyl or aryl substitutions

Q4. Which synthesis route is classically used to prepare barbituric acid derivatives like barbital?

• Condensation of urea with diethyl malonate (malonic ester synthesis)
• Bucherer–Bergs hydantoin synthesis
• Fischer indole synthesis
• Aldol condensation of acetone with urea

Correct Answer: Condensation of urea with diethyl malonate (malonic ester synthesis)

Q5. Barbital belongs to which class of central nervous system depressants?

• Barbiturates
• Benzodiazepines
• Non‑benzodiazepine Z-drugs
• Opioids

Correct Answer: Barbiturates

Q6. Compared to phenobarbital, barbital is generally classified as:

• Less potent and longer acting
• More potent and shorter acting
• Identical in potency and duration
• Short-acting intravenous anesthetic

Correct Answer: Less potent and longer acting

Q7. Which pharmacokinetic property is characteristic of barbital in the body?

• Hepatic metabolism with enterohepatic recycling
• Primarily renal excretion unchanged without metabolism
• Rapid plasma clearance by glomerular filtration only
• Exclusive metabolism by renal tubular secretion

Correct Answer: Hepatic metabolism with enterohepatic recycling

Q8. What major enzymatic effect do barbiturates like barbital have on hepatic drug-metabolizing enzymes?

• Induction of cytochrome P450 enzymes
• Competitive inhibition of CYP3A4 only
• No effect on hepatic enzymes
• Inhibition of phase II conjugation enzymes only

Correct Answer: Induction of cytochrome P450 enzymes

Q9. A classic clinical adverse effect associated with barbiturate overdose is:

• Respiratory depression leading to apnea
• Severe hypertension and tachycardia
• Excessive salivation and lacrimation
• Cholinergic crisis with bradycardia

Correct Answer: Respiratory depression leading to apnea

Q10. Which analytical method is most commonly used for quantitative assay of barbital in formulations and biological samples?

• High-performance liquid chromatography (HPLC)
• Flame photometry
• Turbidimetric titration
• Colorimetric Biuret test

Correct Answer: High-performance liquid chromatography (HPLC)

Q11. Which formulation strategy improves the aqueous solubility of barbital for parenteral use?

• Sodium salt formation (barbital sodium)
• Micronization without salt formation
• Encapsulation in hydrophobic oils only
• Complexation with neutral triglycerides

Correct Answer: Sodium salt formation (barbital sodium)

Q12. The major route of elimination for barbital metabolites is:

• Renal excretion of polar metabolites
• Exhalation as unchanged drug
• Fecal elimination of unchanged drug only
• Sequestration in adipose tissue without elimination

Correct Answer: Renal excretion of polar metabolites

Q13. Which lab test or clinical history would raise concern for prescribing barbital?

• History of acute intermittent porphyria
• Mild seasonal allergic rhinitis
• Controlled hypothyroidism on therapy
• Well-controlled type 2 diabetes on metformin

Correct Answer: History of acute intermittent porphyria

Q14. Which therapeutic use was historically associated with barbital (Veronal)?

• Sedative-hypnotic for insomnia
• First-line antidepressant
• Anti-inflammatory agent for arthritis
• Antipsychotic for schizophrenia

Correct Answer: Sedative-hypnotic for insomnia

Q15. Which structural change typically increases the lipid solubility and rapid onset of barbiturates?

• Introduction of branched alkyl groups at C-5
• Replacement of oxygen with sulfur at C-2
• Hydroxylation of ring nitrogen
• Attachment of polar sulfate group

Correct Answer: Introduction of branched alkyl groups at C-5

Q16. In a toxicity scenario, which treatment is commonly used to enhance elimination of phenobarbital-like compounds and may be applicable to barbital overdose?

• Urinary alkalinization and supportive care
• Administration of naloxone as antidote
• Immediate whole-bowel irrigation only
• Intravascular lipid emulsion as sole therapy

Correct Answer: Urinary alkalinization and supportive care

Q17. Barbiturates potentiate GABA action by which primary mechanism at GABA-A receptors?

• Increasing duration of chloride channel opening
• Increasing frequency of chloride channel opening only
• Direct agonism of GABA binding site
• Blocking chloride channels

Correct Answer: Increasing duration of chloride channel opening

Q18. Which of the following drug interactions is most likely with barbital due to enzyme induction?

• Reduced efficacy of oral anticoagulants like warfarin
• Increased serum concentration of benzodiazepines
• Potentiation of ACE inhibitor blood pressure effects
• Marked increase in digoxin levels

Correct Answer: Reduced efficacy of oral anticoagulants like warfarin

Q19. Which physicochemical test is routinely used in pharmacopeial monographs to confirm identity of barbital?

• Melting point determination and IR spectral analysis
• Optical rotation only
• Chiral HPLC to determine enantiomeric excess
• Kjeldahl nitrogen alone

Correct Answer: Melting point determination and IR spectral analysis

Q20. Which property of barbital contributes to its potential for accumulation in chronic dosing?

• Relatively long elimination half-life and lipid solubility
• Rapid complete renal clearance within hours
• No protein binding in plasma
• Exclusive biliary excretion without reabsorption

Correct Answer: Relatively long elimination half-life and lipid solubility

Q21. Which adverse effect is commonly associated with long-term barbiturate therapy?

• Physical dependence and tolerance
• Hyperactivity and insomnia
• Severe neutropenia in all patients
• Permanent peripheral neuropathy in low doses

Correct Answer: Physical dependence and tolerance

Q22. The absorption of orally administered barbital is best described as:

• Well absorbed from the gastrointestinal tract
• Poorly absorbed unless given as a prodrug
• Only absorbed when given with fatty meals
• Absorption limited by first-pass renal excretion

Correct Answer: Well absorbed from the gastrointestinal tract

Q23. Which laboratory technique is preferred for separation and identification of barbital in complex biological matrices?

• Gas chromatography–mass spectrometry (GC-MS)
• Paper chromatography with ninhydrin detection
• Flame ionization detector without separation
• Atomic absorption spectroscopy

Correct Answer: Gas chromatography–mass spectrometry (GC-MS)

Q24. Which metabolic pathway commonly transforms barbiturates into more polar metabolites?

• Oxidation followed by conjugation (phase I then phase II)
• Direct glucuronidation only without prior oxidation
• Reductive dehalogenation in the kidney
• Cleavage by digestive enzymes in the GI tract

Correct Answer: Oxidation followed by conjugation (phase I then phase II)

Q25. For quality control, which impurity test is important for barbital sodium injection?

• Residual solvent and microbial limit tests
• Heavy metal-free flame test only
• Water content by Karl Fischer not required
• Lack of UV absorbance at 254 nm

Correct Answer: Residual solvent and microbial limit tests

Q26. Which statement about the pharmacodynamics of barbital is correct?

• It depresses the central nervous system dose-dependently
• It produces CNS stimulation at therapeutic doses
• It selectively blocks peripheral nociceptors
• It acts primarily as a serotonin reuptake inhibitor

Correct Answer: It depresses the central nervous system dose-dependently

Q27. Which population group requires extreme caution or avoidance of barbital therapy?

• Patients with a history of substance abuse
• Young healthy adults with no comorbidities
• Individuals with controlled hyperlipidemia only
• Patients using topical antibacterial creams

Correct Answer: Patients with a history of substance abuse

Q28. Which test result would indicate significant plasma protein binding of barbital?

• High percentage bound in ultrafiltrate plasma protein assay
• Rapid urinary excretion of unchanged drug only
• Equal distribution in red blood cells and plasma
• No change in free fraction with albumin concentration changes

Correct Answer: High percentage bound in ultrafiltrate plasma protein assay

Q29. Which is a key difference between barbiturates and benzodiazepines in receptor pharmacology?

• Barbiturates increase chloride channel open duration; benzodiazepines increase frequency
• Benzodiazepines act as direct agonists at GABA site; barbiturates do not bind GABA receptors
• Barbiturates block GABA receptors; benzodiazepines potentiate glutamate
• They have identical mechanisms and binding sites

Correct Answer: Barbiturates increase chloride channel open duration; benzodiazepines increase frequency

Q30. Which storage condition is most appropriate for solid barbital formulations in the pharmacy?

• Cool, dry place protected from light
• Keep frozen at −20°C in airtight container
• Store in bright sunlight to prevent degradation
• High humidity environment is acceptable

Correct Answer: Cool, dry place protected from light

Q31. Which regulatory consideration historically limited the clinical use of barbital?

• High potential for dependence and overdose risks
• Lack of any sedative activity in humans
• Excessive cost compared to placebo
• Universal severe allergic reactions in population

Correct Answer: High potential for dependence and overdose risks

Q32. Which laboratory parameter would be most useful to monitor in a patient on chronic barbital therapy?

• Liver function tests (LFTs)
• Serum amylase only
• Fasting blood glucose exclusively
• Serum potassium levels routinely

Correct Answer: Liver function tests (LFTs)

Q33. Which characteristic differentiates barbital from ultra-short-acting barbiturates used for induction of anesthesia?

• Longer onset and longer duration of action
• Faster redistribution and very short CNS effect
• Rapid hydrolysis by plasma esterases
• Exclusive intravenous use only

Correct Answer: Longer onset and longer duration of action

Q34. Which structural analog of barbital would most likely reduce sedative potency?

• Replacing C-5 alkyl groups with polar substituents
• Increasing C-5 alkyl chain branching
• Adding lipophilic aromatic rings at C-5
• Maintaining the diethyl groups unchanged

Correct Answer: Replacing C-5 alkyl groups with polar substituents

Q35. In toxicology screening, a presumptive positive for barbiturates is commonly performed using:

• Immunoassay (EMIT or similar) followed by confirmatory GC-MS
• Complete blood count as a specific screen
• Urine dipstick for glucose
• Skin patch testing

Correct Answer: Immunoassay (EMIT or similar) followed by confirmatory GC-MS

Q36. Which pharmacological effect makes barbiturates less desirable for insomnia than modern agents?

• Daytime sedation and cognitive impairment due to long half-life
• Totally absent hypnotic effect at therapeutic doses
• They enhance REM sleep to excessive degrees
• They only work when combined with opioids

Correct Answer: Daytime sedation and cognitive impairment due to long half-life

Q37. Which biochemical assay can quantify barbital in pharmaceutical formulations for potency testing?

• HPLC with UV detection against a reference standard
• Gram staining of the sample
• pH meter reading alone
• Color change on Benedict’s reagent

Correct Answer: HPLC with UV detection against a reference standard

Q38. Which interaction is likely when barbital is co-administered with oral contraceptives?

• Reduced contraceptive efficacy due to enzyme induction
• Increased estrogen levels and toxicity
• No interaction expected at all
• Immediate cessation of menstrual cycles in all patients

Correct Answer: Reduced contraceptive efficacy due to enzyme induction

Q39. Which experimental animal model outcome supports barbital’s sedative properties?

• Prolonged pentobarbital-induced sleeping time (potentiation)
• Increased maze-running speed indicating stimulation
• Enhanced conditioned avoidance response always
• Reduced immobility in forced swim test exclusively

Correct Answer: Prolonged pentobarbital-induced sleeping time (potentiation)

Q40. A pharmacy student studying stability should know that degradation of barbital is most likely accelerated by:

• Exposure to strong acids, bases, or heat
• Storage at refrigerated temperatures only
• Packaging under inert gas at low humidity
• Lyophilization to dryness

Correct Answer: Exposure to strong acids, bases, or heat

Q41. Which clinical sign is a warning of early toxicity with sedative-hypnotics like barbital?

• Drowsiness progressing to confusion and ataxia
• Immediate severe myoclonus without other signs
• Sudden sharp chest pain as the first sign
• Acute bright red rash on exposure to light

Correct Answer: Drowsiness progressing to confusion and ataxia

Q42. Which quality control parameter assesses uniformity in a batch of barbital tablets?

• Content uniformity or weight variation test
• Disintegration time only irrespective of content
• Viscosity measurement of the bulk powder
• Optical rotation of the tablet mass

Correct Answer: Content uniformity or weight variation test

Q43. Which property of barbital influences its passage across the blood-brain barrier?

• Lipophilicity and degree of ionization at physiological pH
• Its ability to chelate calcium ions exclusively
• Insolubility in organic solvents only
• Large molecular weight >2000 Da

Correct Answer: Lipophilicity and degree of ionization at physiological pH

Q44. Which contraindication applies to barbiturate therapy including barbital?

• Porphyria and severe respiratory insufficiency
• Uncomplicated seasonal allergies only
• Mild controlled hypertension without comorbidities
• History of migraine headaches exclusively

Correct Answer: Porphyria and severe respiratory insufficiency

Q45. In medicinal chemistry, replacement of oxygen with sulfur at C-2 (thiobarbiturates) typically results in:

• Increased lipid solubility and more rapid onset
• Complete loss of central activity
• Reduced potency with longer duration only
• Enhanced water solubility and slower onset

Correct Answer: Increased lipid solubility and more rapid onset

Q46. Which is a reliable confirmatory test for presence of barbital in a forensic sample?

• Gas chromatography–mass spectrometry (GC-MS) identification
• Thin-layer chromatography only with visual stain
• Simple urine dipstick showing pH change
• Microscopic crystal identification only

Correct Answer: Gas chromatography–mass spectrometry (GC-MS) identification

Q47. Which excipient selection helps improve dissolution rate of a poorly soluble barbital tablet?

• Use of water‑soluble fillers and disintegrants (e.g., MCC, croscarmellose)
• Adding large amounts of hydrophobic waxes
• Decreasing tablet porosity intentionally
• Exclusion of any soluble binders

Correct Answer: Use of water‑soluble fillers and disintegrants (e.g., MCC, croscarmellose)

Q48. Which monitoring is important during prolonged therapy with barbital in epileptic patients?

• Assessment of seizure control and drug plasma levels
• Only monitoring for skin color changes
• Weekly chest X-rays routinely
• No monitoring required once stable dose achieved

Correct Answer: Assessment of seizure control and drug plasma levels

Q49. From a toxicokinetic standpoint, which patient factor increases risk of barbital accumulation?

• Hepatic impairment reducing metabolic clearance
• Young age with hyperactive liver enzymes
• Concurrent use of potent CYP inducers only
• High-protein diet accelerating elimination

Correct Answer: Hepatic impairment reducing metabolic clearance

Q50. Which statement best summarizes the contemporary role of barbital in therapy and education for B.Pharm students?

• Important historically and mechanistically, but largely replaced clinically by safer agents
• It remains the first-line hypnotic in current practice globally
• Barbital has no educational value and is obsolete in all contexts
• Used primarily as an antibiotic in modern therapy

Correct Answer: Important historically and mechanistically, but largely replaced clinically by safer agents

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

Mail- Sachin@pharmacyfreak.com