Ultra-short acting barbiturates – Thiopental sodium MCQs With Answer

Ultra-short acting barbiturates – Thiopental sodium MCQs With Answer

Ultra-short acting barbiturates, especially Thiopental sodium, are key topics in anesthesia pharmacology for B. Pharm students. This focused introduction covers Thiopental’s mechanism, pharmacokinetics, clinical uses, dosing, adverse effects, contraindications, drug interactions and formulation issues. Understanding redistribution, hepatic metabolism, rapid onset and short duration is essential for safe induction of anesthesia and emergency use. These MCQs emphasize applied knowledge for exams and practical pharmacy practice, with clinical scenarios, stability, compatibility and monitoring considerations. Targeted keywords include Ultra-short acting barbiturates, Thiopental sodium, anesthesia, pharmacology, dosing, adverse effects and MCQs for B. Pharm students. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which of the following best describes the primary mechanism of action of Thiopental sodium?

• Blockade of NMDA receptors
• Inhibition of acetylcholine receptors
• Potentiation of GABA-A receptor-mediated chloride influx
• Activation of opioid receptors

Correct Answer: Potentiation of GABA-A receptor-mediated chloride influx

Q2. Thiopental sodium is classified as which type of barbiturate based on duration of action?

• Long-acting barbiturate
• Intermediate-acting barbiturate
• Short-acting barbiturate
• Ultra-short-acting barbiturate

Correct Answer: Ultra-short-acting barbiturate

Q3. The rapid termination of effect after a single IV dose of Thiopental is mainly due to:

• Renal excretion of unchanged drug
• Metabolic breakdown in plasma
• Redistribution from brain to muscle and fat
• Rapid biliary excretion

Correct Answer: Redistribution from brain to muscle and fat

Q4. Typical intravenous induction dose of Thiopental sodium in an adult is:

• 0.5–1 mg/kg
• 3–5 mg/kg
• 10–15 mg/kg
• 20–25 mg/kg

Correct Answer: 3–5 mg/kg

Q5. Which clinical use is NOT an appropriate indication for Thiopental sodium?

• Induction of general anesthesia
• Short procedures requiring rapid recovery
• Chronic long-term sedation in ICU for days
• Control of raised intracranial pressure in acute situations

Correct Answer: Chronic long-term sedation in ICU for days

Q6. A major contraindication for Thiopental use is:

• History of malignant hyperthermia
• Acute intermittent porphyria
• Hypothyroidism
• Mild controlled hypertension

Correct Answer: Acute intermittent porphyria

Q7. Which pharmacokinetic property of Thiopental contributes most to prolonged sedation after repeated dosing?

• High renal clearance
• Accumulation in peripheral tissues (fat)
• Low protein binding
• Rapid hepatic metabolism to active metabolites

Correct Answer: Accumulation in peripheral tissues (fat)

Q8. Thiopental sodium increases duration of chloride channel opening at GABA-A receptors. At very high concentrations it may also:

• Act as a competitive GABA antagonist
• Directly activate GABA-A receptors in absence of GABA
• Stimulate glutamate release
• Block sodium channels preferentially

Correct Answer: Directly activate GABA-A receptors in absence of GABA

Q9. Which physiologic effect is commonly seen after induction with Thiopental?

• Sympathetic stimulation and hypertension
• Respiratory stimulation and tachypnea
• Respiratory depression and hypotension
• Bradycardia with hypertension

Correct Answer: Respiratory depression and hypotension

Q10. Thiopental is supplied commercially as a sodium salt because:

• It increases water solubility for intravenous administration
• It improves taste for oral use
• It reduces potency to minimize side effects
• It prevents protein binding

Correct Answer: It increases water solubility for intravenous administration

Q11. Which laboratory monitoring is most important immediately after Thiopental induction?

• Liver function tests
• Continuous pulse oximetry and capnography
• Serum electrolytes
• Complete blood count

Correct Answer: Continuous pulse oximetry and capnography

Q12. Thiopental compared to propofol for induction is characterized by:

• Faster recovery and less hangover
• Less respiratory depression
• Less antiemetic properties
• More prolonged accumulation after repeated doses

Correct Answer: More prolonged accumulation after repeated doses

Q13. Which statement about Thiopental metabolism is correct?

• It is primarily renally excreted unchanged
• It undergoes hepatic oxidative metabolism by microsomal enzymes
• It is metabolized by plasma esterases
• It is not metabolized and is exhaled unchanged

Correct Answer: It undergoes hepatic oxidative metabolism by microsomal enzymes

Q14. A pharmacist advising on storage should recommend that reconstituted Thiopental solution be:

• Stored at room temperature indefinitely
• Discarded if not used within manufacturer’s recommended time due to instability
• Frozen for long-term stability
• Mixed with acidic solutions to maintain potency

Correct Answer: Discarded if not used within manufacturer’s recommended time due to instability

Q15. Which adverse effect is especially important when Thiopental is given rapidly IV?

• Severe hypertension
• Venous thrombosis
• Apnea and profound respiratory depression
• Acute renal failure

Correct Answer: Apnea and profound respiratory depression

Q16. Thiopental reduces intracranial pressure primarily by:

• Increasing cerebrospinal fluid production
• Causing cerebral vasoconstriction and lowering cerebral blood flow
• Blocking sodium channels in neurons
• Increasing intracranial blood volume

Correct Answer: Causing cerebral vasoconstriction and lowering cerebral blood flow

Q17. Which drug interaction is MOST important to consider when administering Thiopental?

• Concurrent beta-blocker use leading to tachycardia
• Concurrent benzodiazepines potentiating CNS depression
• Antacids reducing its absorption
• Concurrent insulin causing hypoglycemia

Correct Answer: Concurrent benzodiazepines potentiating CNS depression

Q18. In acute porphyria, Thiopental is contraindicated because it:

• Directly damages erythrocytes
• Induces hepatic enzymes and exacerbates porphyrin synthesis
• Causes severe renal vasoconstriction
• Competes with heme for binding sites

Correct Answer: Induces hepatic enzymes and exacerbates porphyrin synthesis

Q19. Which barbiturate is most similar to Thiopental in clinical use for induction?

• Phenobarbital
• Secobarbital
• Methohexital
• Amobarbital

Correct Answer: Methohexital

Q20. Thiopental is lipid soluble. This property primarily explains its:

• High urinary excretion
• Rapid onset of action
• Inability to cross blood-brain barrier
• Low potency

Correct Answer: Rapid onset of action

Q21. Which is a common formulation consideration for Thiopental sodium injection?

• Prepared at acidic pH to increase stability
• Contains organic solvent as alkaline solution which may precipitate with acidic drugs
• Can be mixed directly with any IV fluid without compatibility checks
• Is formulated for intramuscular administration preferentially

Correct Answer: Contains organic solvent as alkaline solution which may precipitate with acidic drugs

Q22. Which effect on EEG is typically observed after Thiopental administration?

• Marked activation and increased high-frequency activity
• Progressive slowing and burst-suppression at high doses
• No change in EEG patterns
• Isoelectric line immediately at clinical doses

Correct Answer: Progressive slowing and burst-suppression at high doses

Q23. In dosing a hypovolemic patient, the induction dose of Thiopental should be:

• Increased due to decreased sensitivity
• Reduced due to enhanced cardiovascular depression risk
• Unchanged regardless of volume status
• Given as a continuous infusion only

Correct Answer: Reduced due to enhanced cardiovascular depression risk

Q24. The onset of unconsciousness after IV Thiopental is approximately:

• 30–45 seconds
• 10–15 minutes
• 1–2 hours
• 5–10 minutes

Correct Answer: 30–45 seconds

Q25. Which statement about protein binding of Thiopental is true?

• It is minimally protein bound (<10%)
• It is highly protein bound, affecting its free concentration
• It binds exclusively to red blood cells
• Protein binding is irrelevant for distribution

Correct Answer: It is highly protein bound, affecting its free concentration

Q26. Which one of the following is a desirable property of an induction agent that Thiopental provides?

• Strong analgesic effect for surgery
• Rapid and smooth loss of consciousness
• Minimal effect on respiratory drive
• Long duration suitable for long surgeries

Correct Answer: Rapid and smooth loss of consciousness

Q27. Which monitoring parameter is most useful to assess depth of anesthesia after Thiopental induction?

• Serum Thiopental concentration bedside test
• Clinical signs and electroencephalogram-derived indices
• Arterial blood pH only
• Urine color

Correct Answer: Clinical signs and electroencephalogram-derived indices

Q28. Which of the following is a potential complication if Thiopental extravasates during IV injection?

• Local tissue necrosis and inflammation
• Systemic allergic anaphylaxis only
• Immediate systemic hypertension
• Renal stone formation

Correct Answer: Local tissue necrosis and inflammation

Q29. In which patient population should Thiopental be used with caution due to slower redistribution and elimination?

• Young healthy adults
• Elderly patients with reduced lean body mass
• Patients with acute infections
• Patients on short courses of antibiotics

Correct Answer: Elderly patients with reduced lean body mass

Q30. Thiopental’s effect on cardiovascular system includes:

• Increase in systemic vascular resistance
• Myocardial stimulation and tachycardia
• Negative inotropic effect and vasodilation causing hypotension
• Selective coronary vasoconstriction improving perfusion

Correct Answer: Negative inotropic effect and vasodilation causing hypotension

Q31. Which is TRUE regarding Thiopental and pregnancy?

• It is completely safe with no fetal effects
• It crosses the placenta and may cause neonatal respiratory depression
• It is preferred for long-term obstetric analgesia
• It does not affect uterine tone

Correct Answer: It crosses the placenta and may cause neonatal respiratory depression

Q32. Which is the major route of elimination for Thiopental metabolites?

• Biliary excretion of unchanged drug
• Urinary excretion of polar metabolites after hepatic metabolism
• Exhalation via lungs unchanged
• Sequestration into bone

Correct Answer: Urinary excretion of polar metabolites after hepatic metabolism

Q33. Which laboratory test might be altered by chronic barbiturate therapy due to enzyme induction?

• Serum creatinine only
• Liver function tests and drug levels of co-administered drugs
• Hemoglobin electrophoresis
• Serum amylase exclusively

Correct Answer: Liver function tests and drug levels of co-administered drugs

Q34. Which clinical scenario favors choosing Thiopental over inhalation induction?

• Patient with severe airway obstruction
• Need for rapid, single-shot induction in hemodynamically stable adult
• Need for precise titratable sedation over many hours
• Patient allergic to all intravenous agents

Correct Answer: Need for rapid, single-shot induction in hemodynamically stable adult

Q35. Which symptom is commonly associated with Thiopental overdose?

• Severe bronchospasm only
• Profound respiratory depression and coma
• Isolated hypertension with tachyarrhythmia
• Severe pruritus without sedation

Correct Answer: Profound respiratory depression and coma

Q36. Which of the following best describes Thiopental’s effect on cerebral metabolic rate?

• Increases cerebral metabolic rate
• No effect on cerebral metabolism
• Decreases cerebral metabolic rate and oxygen consumption
• Causes paradoxical increase in brain oxygen demand

Correct Answer: Decreases cerebral metabolic rate and oxygen consumption

Q37. Which factor increases the free fraction of Thiopental in plasma?

• Hypoalbuminemia
• Hyperalbuminemia
• Increased red blood cell count
• Alkaline urinary pH

Correct Answer: Hypoalbuminemia

Q38. For electroconvulsive therapy (ECT), which property of Thiopental is relevant?

• It lengthens seizure duration significantly
• It is ideal because it increases seizure threshold substantially
• It shortens seizure duration and may reduce ECT efficacy compared to methohexital
• It has no effect on seizure threshold

Correct Answer: It shortens seizure duration and may reduce ECT efficacy compared to methohexital

Q39. Which storage precaution is important for Thiopental powder vials?

• Store in light-exposed area to maintain potency
• Protect from light and store according to manufacturer temperature recommendations
• Freeze to extend shelf life indefinitely
• Keep in acidic solution to stabilize

Correct Answer: Protect from light and store according to manufacturer temperature recommendations

Q40. Which of the following is TRUE about the pH of Thiopental sodium solution?

• It is highly acidic (pH around 2)
• It is neutral (pH 7)
• It is alkaline which can cause precipitation with acidic drugs
• It becomes more stable in acidic environments

Correct Answer: It is alkaline which can cause precipitation with acidic drugs

Q41. Which clinical monitoring sign suggests inadequate ventilation after Thiopental induction?

• Brisk pupil reactivity
• Rising end-tidal CO2 and falling oxygen saturation
• Stable blood pressure and heart rate
• Muscle fasciculations only

Correct Answer: Rising end-tidal CO2 and falling oxygen saturation

Q42. Which practice reduces risk of severe hypotension after Thiopental induction?

• Administering a rapid large IV bolus without fluids
• Preloading with intravenous fluids and titrating dose slowly
• Using Thiopental without airway management
• Mixing with other CNS stimulants

Correct Answer: Preloading with intravenous fluids and titrating dose slowly

Q43. Which organ impairment requires dose adjustment and extra caution with Thiopental?

• Mild seasonal allergies
• Severe hepatic impairment
• Uncomplicated skin rash
• Localized tendon injury

Correct Answer: Severe hepatic impairment

Q44. Which statement about Thiopental and enzyme induction is correct?

• Thiopental inhibits cytochrome P450 enzymes
• Thiopental is an inducer of hepatic microsomal enzymes
• Thiopental has no effect on drug metabolism
• Thiopental reduces clearance of other drugs by direct competition

Correct Answer: Thiopental is an inducer of hepatic microsomal enzymes

Q45. Which of the following is an advantage of Thiopental in neuroanesthesia?

• It increases intracranial pressure
• It lowers cerebral metabolic rate and intracranial pressure
• It causes cerebral vasodilation
• It guarantees complete analgesia

Correct Answer: It lowers cerebral metabolic rate and intracranial pressure

Q46. Which statement about allergic reactions to Thiopental is correct?

• True anaphylaxis to Thiopental never occurs
• Anaphylactic reactions are possible and require immediate treatment
• Only topical allergy is possible
• Allergic reactions always present as delayed skin rashes

Correct Answer: Anaphylactic reactions are possible and require immediate treatment

Q47. Which intravenous fluid is generally compatible with Thiopental for administration?

• Any acidic solution including 5% dextrose with low pH
• Alkaline compatible solutions as recommended by manufacturer; always check compatibility
• Strongly acidic drugs to stabilize formulation
• Mixing with calcium-containing solutions is always safe

Correct Answer: Alkaline compatible solutions as recommended by manufacturer; always check compatibility

Q48. For overdose management of Thiopental, the most important immediate step is:

• Administer intravenous naloxone
• Support airway, ventilation and circulation
• Give oral activated charcoal
• Induce emesis

Correct Answer: Support airway, ventilation and circulation

Q49. Which clinical sign indicates too deep anesthesia after Thiopental administration?

• Spontaneous purposeful movement
• Marked hypotension, absent corneal reflexes and very low BIS values
• Slight pallor with stable vitals
• Alertness and following commands

Correct Answer: Marked hypotension, absent corneal reflexes and very low BIS values

Q50. Which safety counseling point should a pharmacist give regarding discharge after procedures using Thiopental?

• Patients can drive immediately after discharge
• A responsible adult should escort the patient and avoid driving for 24 hours
• No special precautions are needed
• Patients should avoid fluids for 48 hours

Correct Answer: A responsible adult should escort the patient and avoid driving for 24 hours

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