Ultra-short acting barbiturates – Thiamylal sodium MCQs With Answer

Ultra-short acting barbiturates – Thiamylal sodium MCQs With Answer

This concise, SEO-friendly introduction helps B.Pharm students master ultra-short acting barbiturates with a focus on Thiamylal sodium. Learn key concepts in pharmacology, mechanism of action at GABAA receptors, pharmacokinetics (rapid onset, redistribution), clinical uses such as anesthesia induction, adverse effects like respiratory depression and hypotension, metabolism and drug interactions, contraindications including porphyria, and safety considerations in special populations. These targeted MCQs reinforce core topics for exams and practical pharmacy practice. Clear, exam-oriented questions and answers build deep understanding for safe therapeutic use and critical thinking. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which class of drug does thiamylal sodium belong to?

• Ultra-short acting barbiturate
• Benzodiazepine
• Opioid analgesic
• Local anesthetic

Correct Answer: Ultra-short acting barbiturate

Q2. The primary mechanism of action of thiamylal involves modulation of which receptor?

• Nicotinic acetylcholine receptor
• GABAA receptor
• NMDA receptor
• Mu-opioid receptor

Correct Answer: GABAA receptor

Q3. Which physiochemical feature largely explains the rapid onset of thiamylal?

• High water solubility
• High lipid solubility
• High molecular weight
• Strong ionic charge at physiological pH

Correct Answer: High lipid solubility

Q4. The short duration of action of thiamylal after a single IV dose is mainly due to:

• Rapid renal excretion
• Redistribution from brain to peripheral tissues
• Slow hepatic metabolism
• Active reuptake into plasma proteins

Correct Answer: Redistribution from brain to peripheral tissues

Q5. Thiamylal is classified chemically as a:

• Thiobarbiturate
• Oxybarbiturate
• Benzimidazole
• Imidazoline

Correct Answer: Thiobarbiturate

Q6. The clinical use of thiamylal most commonly includes:

• Induction of general anesthesia
• Chronic outpatient insomnia therapy
• Treatment of acute asthma attacks
• Management of neuropathic pain

Correct Answer: Induction of general anesthesia

Q7. Compared to oxybarbiturates, thiobarbiturates like thiamylal generally show:

• Lower lipid solubility and slower onset
• Greater lipid solubility and more rapid onset
• Greater renal elimination unchanged
• Selective activity at NMDA receptors

Correct Answer: Greater lipid solubility and more rapid onset

Q8. Which adverse effect is most commonly associated with thiamylal during induction?

• Severe hypertension
• Respiratory depression and apnea
• Bronchospasm
• Hyperglycemia

Correct Answer: Respiratory depression and apnea

Q9. Thiamylal’s interaction profile includes induction of which hepatic system with chronic use?

• CYP450 enzyme system
• Monoamine oxidase system
• Renal transporters only
• ATP-binding cassette transporters exclusively

Correct Answer: CYP450 enzyme system

Q10. Thiamylal is contraindicated in patients with which condition?

• Acute intermittent porphyria
• Essential hypertension
• Hypothyroidism
• Hyperlipidemia

Correct Answer: Acute intermittent porphyria

Q11. The most appropriate immediate management for a patient with thiamylal-induced apnea is:

• Administer flumazenil
• Airway support and mechanical ventilation
• Give naloxone
• Induce emesis

Correct Answer: Airway support and mechanical ventilation

Q12. Which statement about thiamylal metabolism is correct?

• It is primarily metabolized in the liver to inactive metabolites
• It is mainly excreted unchanged in urine
• It undergoes extensive renal tubular reabsorption unchanged
• It is activated by hepatic enzymes into a more potent metabolite

Correct Answer: It is primarily metabolized in the liver to inactive metabolites

Q13. Protein binding of thiamylal is important clinically because:

• High protein binding reduces brain penetration entirely
• Changes in plasma protein levels alter free drug concentration
• Protein binding prevents hepatic metabolism
• Protein binding increases urinary excretion

Correct Answer: Changes in plasma protein levels alter free drug concentration

Q14. Thiamylal increases the duration of chloride channel opening at GABAA receptors, resulting in:

• Neuronal excitation
• Neuronal inhibition and sedation
• Enhanced glutamate release
• Increased intracellular cAMP

Correct Answer: Neuronal inhibition and sedation

Q15. Which monitoring parameter is essential during thiamylal administration?

• Electrolyte panel every 5 minutes
• Continuous respiratory and cardiovascular monitoring
• Regular blood cultures
• Serial spirometry measurements pre-dose only

Correct Answer: Continuous respiratory and cardiovascular monitoring

Q16. Thiamylal crosses the placenta. The clinical implication is:

• No fetal effects due to placental barrier
• Potential neonatal respiratory depression if given near delivery
• Enhanced fetal growth
• Therapeutic fetal sedation during labor

Correct Answer: Potential neonatal respiratory depression if given near delivery

Q17. In which patient population is dose reduction of thiamylal often necessary?

• Young healthy adults
• Elderly patients with decreased hepatic function
• Patients with acute bacterial infections

Correct Answer: Elderly patients with decreased hepatic function

Q18. Which of the following is NOT a typical clinical use of thiamylal?

• Anesthesia induction
• Treating status epilepticus as a first-line outpatient therapy
• Short procedural sedation in controlled settings
• Adjunct in surgical anesthesia

Correct Answer: Treating status epilepticus as a first-line outpatient therapy

Q19. Which laboratory abnormality may be observed with chronic barbiturate use due to enzyme induction?

• Decreased clearance of warfarin
• Decreased plasma levels of oral contraceptives
• Marked hyperkalemia
• Persistent hypoglycemia

Correct Answer: Decreased plasma levels of oral contraceptives

Q20. Which statement about cross-tolerance with barbiturates and other CNS depressants is true?

• No cross-tolerance with alcohol exists
• There is cross-tolerance between barbiturates and alcohol/benzodiazepines
• Cross-tolerance makes combinations entirely safe
• Cross-tolerance only occurs with opioids

Correct Answer: There is cross-tolerance between barbiturates and alcohol/benzodiazepines

Q21. Which of the following is an important contraindication when using thiamylal?

• Porphyria
• Migraine headaches
• Controlled hypotension
• Myopia

Correct Answer: Porphyria

Q22. During overdose of thiamylal, which antidote is useful?

• Flumazenil
• Naloxone
• There is no specific antidote; treatment is supportive
• Physostigmine

Correct Answer: There is no specific antidote; treatment is supportive

Q23. Which property of thiamylal limits the effectiveness of hemodialysis in overdose?

• Low protein binding
• High lipid solubility and high protein binding
• High water solubility
• Rapid renal clearance of unchanged drug

Correct Answer: High lipid solubility and high protein binding

Q24. Thiamylal is commonly supplied and administered by which route in anesthesia?

• Intravenous injection
• Oral tablet
• Subcutaneous infusion
• Inhalational vapor

Correct Answer: Intravenous injection

Q25. When considering compatibility, thiamylal should be mixed with which type of solutions cautiously due to precipitation risk?

• Strong acids and certain electrolytes causing incompatibility
• Sterile water only
• 100% ethanol exclusively
• All lipid emulsions are completely safe

Correct Answer: Strong acids and certain electrolytes causing incompatibility

Q26. The term “redistribution” in the context of thiamylal pharmacokinetics refers to:

• Movement of drug from blood to fat and muscle decreasing CNS levels
• Hepatic metabolism to active metabolites
• Renal reabsorption into plasma
• Excretion of unchanged drug into bile

Correct Answer: Movement of drug from blood to fat and muscle decreasing CNS levels

Q27. Which monitoring is important in prolonged infusion of thiamylal in ICU sedation?

• Daily liver function tests and renal monitoring
• No monitoring is needed for prolonged infusions
• Only blood glucose monitoring
• Only electrolyte monitoring

Correct Answer: Daily liver function tests and renal monitoring

Q28. Thiamylal’s pharmacodynamic effect on the cardiovascular system typically includes:

• Marked tachycardia with hypertension
• Myocardial ischemia as the primary effect
• Dose-dependent hypotension due to vasodilation
• Direct increase in cardiac contractility

Correct Answer: Dose-dependent hypotension due to vasodilation

Q29. In comparing thiamylal and thiopental, which is a reasonable general statement?

• Both are ultra-short acting thiobarbiturates used for induction
• Thiopental is an opioid, thiamylal is not
• Thiamylal is orally administered while thiopental is IV only
• Both are benzodiazepines

Correct Answer: Both are ultra-short acting thiobarbiturates used for induction

Q30. Which factor increases the free (active) fraction of thiamylal in plasma?

• Hypoalbuminemia
• Hyperalbuminemia
• High plasma calcium only
• Low lipid solubility

Correct Answer: Hypoalbuminemia

Q31. Which of the following best explains why thiamylal is not preferred for maintenance of long-term sedation?

• Prolonged sedation due to accumulation in fat and altered kinetics
• It has no sedative properties
• It is only effective orally
• It cannot be reversed by any means

Correct Answer: Prolonged sedation due to accumulation in fat and altered kinetics

Q32. Which is a recognized pharmacodynamic interaction with thiamylal?

• Synergistic CNS depression with opioids and benzodiazepines
• Antagonism of opioid analgesia
• Reduced effect of inhalational anesthetics
• Enhancement of platelet aggregation

Correct Answer: Synergistic CNS depression with opioids and benzodiazepines

Q33. Which clinical sign suggests acute barbiturate toxicity in a patient after thiamylal administration?

• Hyperreflexia and agitation
• Coma with depressed respiration and pinpoint pupils
• Hypotension with bradypnea and reduced consciousness
• Isolated severe rash without CNS effects

Correct Answer: Hypotension with bradypnea and reduced consciousness

Q34. In patients with hepatic impairment, thiamylal dosing should be:

• Unchanged because liver is not involved
• Reduced due to decreased metabolism risk
• Increased to overcome protein binding
• Switched to oral therapy

Correct Answer: Reduced due to decreased metabolism risk

Q35. Which regulatory consideration is most relevant to thiamylal?

• It is a controlled substance with potential for abuse and dependence
• It is available over the counter
• It is exempt from scheduling due to low risk
• It is banned worldwide for all uses

Correct Answer: It is a controlled substance with potential for abuse and dependence

Q36. Which pharmacokinetic parameter primarily determines initial speed of onset for IV thiamylal?

• Renal clearance
• Lipid solubility and rate of CNS uptake
• Urinary pH
• Volume of distribution in bone

Correct Answer: Lipid solubility and rate of CNS uptake

Q37. Which clinical test can be affected by barbiturates such as thiamylal due to enzyme induction?

• Increased INR in warfarin-treated patients
• Decreased plasma levels of some antiepileptics
• False-positive urine glucose only
• Elevated serum troponin unrelated to cardiac injury

Correct Answer: Decreased plasma levels of some antiepileptics

Q38. Which statement about thiamylal storage and handling is true?

• It is light- and temperature-sensitive and should be stored as per manufacturer guidelines
• It is indefinitely stable at room temperature without precautions
• It must be frozen before use
• It can be stored in direct sunlight

Correct Answer: It is light- and temperature-sensitive and should be stored as per manufacturer guidelines

Q39. Which of the following best describes the effect of alkalinizing urine in barbiturate poisoning?

• Urinary alkalinization enhances excretion of phenobarbital but has limited effect on ultra-short thiobarbiturates
• Alkalinization converts thiamylal into a more toxic compound
• Alkalinization prevents hepatic metabolism completely
• Urinary alkalinization is the primary antidote for thiamylal

Correct Answer: Urinary alkalinization enhances excretion of phenobarbital but has limited effect on ultra-short thiobarbiturates

Q40. Which structural feature distinguishes thiobarbiturates like thiamylal from oxybarbiturates?

• Presence of a sulfur atom in place of oxygen at C2
• An extra hydroxyl group at the aromatic ring
• Absence of a barbituric acid core
• Incorporation of a benzene sulfonamide

Correct Answer: Presence of a sulfur atom in place of oxygen at C2

Q41. Thiamylal produces anesthesia primarily by:

• Blocking voltage-gated sodium channels selectively
• Enhancing inhibitory GABAergic neurotransmission and reducing excitatory transmission
• Directly activating opioid receptors to induce unconsciousness
• Increasing dopamine release in the basal ganglia

Correct Answer: Enhancing inhibitory GABAergic neurotransmission and reducing excitatory transmission

Q42. Which factor most increases the risk of prolonged recovery after thiamylal induction?

• Short duration of anesthesia
• Obesity with increased adipose tissue for drug redistribution
• Young age with fast metabolism
• High plasma albumin levels

Correct Answer: Obesity with increased adipose tissue for drug redistribution

Q43. In the context of dosing, a typical principle for induction dosing of thiamylal is to:

• Give frequent small oral doses
• Administer an appropriate single IV bolus based on weight
• Infuse slowly subcutaneously
• Use it only as continuous infusion without bolus

Correct Answer: Administer an appropriate single IV bolus based on weight

Q44. Which symptom is a hallmark of withdrawal from chronic barbiturate use?

• Severe anxiety, tremors, seizures, and possible delirium
• Mild cough and nasal congestion
• Improved sleep and euphoria
• Isolated hypertension without CNS effects

Correct Answer: Severe anxiety, tremors, seizures, and possible delirium

Q45. Which precaution is most important when combining thiamylal with opioid analgesics?

• No precautions are necessary
• Monitor closely for additive respiratory depression and hypotension
• Expect complete reversal of opioid effects
• Opioids eliminate thiamylal from the body faster

Correct Answer: Monitor closely for additive respiratory depression and hypotension

Q46. Which pharmacologic effect would be least expected after therapeutic doses of thiamylal?

• Analgesia comparable to morphine
• Sedation and hypnosis
• Amnesia for induction period
• Decreased cerebral metabolic rate

Correct Answer: Analgesia comparable to morphine

Q47. Thiamylal’s lipid solubility contributes to all of the following EXCEPT:

• Rapid CNS uptake and quick loss of consciousness
• Short initial duration due to redistribution
• Increased urinary excretion of unchanged drug
• Prolonged recovery with repeated dosing due to accumulation in fat

Correct Answer: Increased urinary excretion of unchanged drug

Q48. Which of the following describes an important teaching point for pharmacists counselling about thiamylal use perioperatively?

• Explain potential for transient respiratory depression and monitoring in recovery
• Advise unsupervised use at home for sleep
• Recommend doubling the dose if sedation seems inadequate
• Inform that no monitoring is required after administration

Correct Answer: Explain potential for transient respiratory depression and monitoring in recovery

Q49. Which monitoring sign indicates adequate depth of anesthesia shortly after thiamylal induction?

• Patient actively talking and following commands
• Loss of eyelash reflex and lack of purposeful movement with surgical stimulus
• Marked hypertension and tachycardia alone
• Persistent cough and gag reflex

Correct Answer: Loss of eyelash reflex and lack of purposeful movement with surgical stimulus

Q50. For exam preparation, which study focus will best help B.Pharm students understand thiamylal clinically?

• Pharmacology of GABAA modulation, PK (redistribution), clinical use in induction, adverse effects, interactions and contraindications
• Only the chemical synthesis steps and lab techniques
• Only marketing and brand names without pharmacology
• Only veterinary uses without human pharmacology

Correct Answer: Pharmacology of GABAA modulation, PK (redistribution), clinical use in induction, adverse effects, interactions and contraindications

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.

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