Introduction: Barbiturate poisoning is a critical topic for B. Pharm students, covering overdose presentation, pharmacokinetics, and evidence-based management. Symptoms range from sedation and ataxia to severe respiratory depression, hypotension, coma and metabolic derangements. Management principles include airway protection, ventilatory support, cardiovascular stabilization, decontamination (activated charcoal, sometimes multi‑dose), enhanced elimination (urinary alkalinization, hemodialysis for phenobarbital), and monitoring for complications. Understanding drug interactions, differences between ultra‑short, short, and long‑acting barbiturates, and recognizing when antidotes like naloxone or flumazenil are ineffective is essential. This set focuses on clinical reasoning, toxicokinetics and practical treatment steps. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What is the primary molecular mechanism by which barbiturates produce CNS depression?
- Blockade of NMDA glutamate receptors
- Increase in frequency of GABA-A receptor chloride channel opening
- Increase in duration of GABA-A receptor chloride channel opening
- Direct agonism at dopamine receptors
Correct Answer: Increase in duration of GABA-A receptor chloride channel opening
Q2. Which classical clinical features best describe acute severe barbiturate poisoning?
- Fever, mydriasis, hypertension
- Coma, respiratory depression, hypotension
- Severe agitation, tachycardia, diaphoresis
- Localized muscle weakness without CNS depression
Correct Answer: Coma, respiratory depression, hypotension
Q3. Which barbiturate is long-acting and most amenable to enhanced elimination techniques like urinary alkalinization and hemodialysis?
- Thiopental
- Secobarbital
- Phenobarbital
- Pentobarbital
Correct Answer: Phenobarbital
Q4. The first and most critical step in the emergency management of severe barbiturate overdose is:
- Administration of flumazenil
- Immediate gastric lavage without airway protection
- Secure airway and provide ventilatory support
- Begin urinary alkalinization in the ambulance
Correct Answer: Secure airway and provide ventilatory support
Q5. Which statement about naloxone in suspected barbiturate poisoning is correct?
- Naloxone is the antidote of choice for barbiturate overdose
- Naloxone may partially reverse barbiturate-induced respiratory depression
- Naloxone is ineffective for barbiturate poisoning and should not be relied upon
- Naloxone potentiates barbiturate metabolism via CYP induction
Correct Answer: Naloxone is ineffective for barbiturate poisoning and should not be relied upon
Q6. For phenobarbital overdose, which decontamination technique is especially useful to increase drug elimination?
- Single-dose activated charcoal only
- Multi-dose activated charcoal
- Whole bowel irrigation only for enteric-coated tablets
- Gastric lavage at any time after ingestion
Correct Answer: Multi-dose activated charcoal
Q7. Why is urinary alkalinization used in phenobarbital poisoning?
- Phenobarbital is a weak acid; alkalinization increases its ionization and renal excretion
- It increases hepatic metabolism of phenobarbital via pH-dependent enzymes
- It enhances gastrointestinal absorption to expedite onset of action
- It binds phenobarbital in the urine preventing reabsorption in the bladder
Correct Answer: Phenobarbital is a weak acid; alkalinization increases its ionization and renal excretion
Q8. Which of the following is the best indication for hemodialysis in barbiturate poisoning?
- Mild sedation with normal vital signs
- Severe phenobarbital toxicity with prolonged coma, refractory hypotension, or persistently high levels
- Short-acting barbiturate ingestion within 5 minutes
- Routine care for all barbiturate overdoses regardless of agent
Correct Answer: Severe phenobarbital toxicity with prolonged coma, refractory hypotension, or persistently high levels
Q9. Which clinical sign is least consistent with acute barbiturate overdose?
- Hypoventilation
- Hypothermia
- Hyperreflexia and marked hyperactivity
- Hypotension
Correct Answer: Hyperreflexia and marked hyperactivity
Q10. The primary acid–base disturbance expected in an unresuscitated patient with severe barbiturate-induced respiratory depression is:
- Metabolic alkalosis
- Respiratory alkalosis
- Respiratory acidosis
- Normal acid–base status
Correct Answer: Respiratory acidosis
Q11. Which of the following drug interactions most increases the risk of fatal CNS depression in a patient taking barbiturates?
- Concurrent use of NSAIDs
- Concurrent use of benzodiazepines or ethanol
- Concurrent use of beta‑blockers
- Concurrent use of metformin
Correct Answer: Concurrent use of benzodiazepines or ethanol
Q12. Regarding flumazenil, the benzodiazepine antagonist, which statement is correct in the context of suspected sedative overdose?
- Flumazenil reliably reverses barbiturate toxicity
- Flumazenil is indicated when benzodiazepine overdose is suspected but is ineffective against barbiturates and may precipitate seizures
- Flumazenil should be given routinely to all comatose patients
- Flumazenil enhances renal clearance of barbiturates
Correct Answer: Flumazenil is indicated when benzodiazepine overdose is suspected but is ineffective against barbiturates and may precipitate seizures
Q13. Which factor most increases the likelihood of fatality after barbiturate overdose?
- Young age alone with no co-ingestants
- Co-ingestion of other CNS depressants such as alcohol or opioids
- Early presentation to the emergency department
- Ingestion of ultra-short acting barbiturate alone in small dose
Correct Answer: Co-ingestion of other CNS depressants such as alcohol or opioids
Q14. During monitoring of a patient with suspected barbiturate overdose, which parameter requires the most urgent continuous monitoring?
- Serum cholesterol
- Respiratory rate and oxygen saturation
- Serum amylase
- Fasting blood glucose
Correct Answer: Respiratory rate and oxygen saturation
Q15. Which electrocardiographic or hemodynamic disturbance is commonly seen in severe barbiturate poisoning?
- Severe rapid atrial fibrillation as primary feature
- Progressive hypotension due to peripheral vasodilation and myocardial depression
- Marked QT prolongation as the earliest sign
- Complete heart block in all cases
Correct Answer: Progressive hypotension due to peripheral vasodilation and myocardial depression
Q16. Which barbiturate is classified as ultra‑short acting and often used for induction of anesthesia?
- Phenobarbital
- Thiopental (thiobarbiturate)
- Amobarbital
- Mephobarbital
Correct Answer: Thiopental (thiobarbiturate)
Q17. Hypotension in barbiturate overdose is primarily due to:
- Excessive renal sodium loss
- Peripheral vasodilation and decreased myocardial contractility
- Severe hypertension followed by reflex bradycardia
- Direct stimulation of the vagus nerve causing asystole
Correct Answer: Peripheral vasodilation and decreased myocardial contractility
Q18. Administration of intravenous sodium bicarbonate in phenobarbital poisoning helps by:
- Neutralizing gastric acid to prevent further absorption
- Alkalinizing urine to enhance renal elimination of phenobarbital
- Directly binding phenobarbital in plasma
- Converting phenobarbital to an inactive metabolite in the liver
Correct Answer: Alkalinizing urine to enhance renal elimination of phenobarbital
Q19. Regarding gastric lavage in barbiturate overdose, the most appropriate statement is:
- It is indicated for all ingestions regardless of time since ingestion
- It should be performed only when airway is protected and typically within one hour of a life‑threatening ingestion
- It is more effective than activated charcoal in eliminating phenobarbital
- It is contraindicated in any sedated patient
Correct Answer: It should be performed only when airway is protected and typically within one hour of a life‑threatening ingestion
Q20. Which clinical finding is a predictor of poor outcome in barbiturate overdose?
- Mild transient drowsiness resolving within an hour
- Prolonged coma requiring mechanical ventilation and refractory hypotension
- Normal vital signs with isolated dizziness
- Single episode of vomiting with rapid recovery
Correct Answer: Prolonged coma requiring mechanical ventilation and refractory hypotension
Q21. Barbiturate-induced coma results from depression of which neural structure or system?
- Cerebellar Purkinje cells exclusively
- Reticular activating system and widespread cerebral cortical inhibition
- Peripheral motor neurons only
- Spinal reflex arcs without cortical involvement
Correct Answer: Reticular activating system and widespread cerebral cortical inhibition
Q22. Which statement about phenobarbital pharmacology is false?
- Phenobarbital is metabolized by the liver
- Phenobarbital induces hepatic cytochrome P450 enzymes
- Phenobarbital has significant enterohepatic recirculation in some patients
- Phenobarbital is not protein bound and is freely filtered unchanged by the kidney in all cases
Correct Answer: Phenobarbital is not protein bound and is freely filtered unchanged by the kidney in all cases
Q23. Multi‑dose activated charcoal is particularly indicated for which scenario?
- Single small-dose ingestion of an ultra‑short acting barbiturate with rapid recovery
- Phenobarbital overdose to interrupt enterohepatic recirculation and enhance elimination
- When patient presents more than 48 hours after ingestion
- In all patients regardless of the ingested drug
Correct Answer: Phenobarbital overdose to interrupt enterohepatic recirculation and enhance elimination
Q24. Barbiturate withdrawal after chronic use can present with which dangerous complication?
- Bradycardia without CNS symptoms
- Seizures and autonomic instability
- Isolated mild insomnia only
- Permanent neuromuscular paralysis
Correct Answer: Seizures and autonomic instability
Q25. The mechanism by which multi‑dose activated charcoal speeds elimination of phenobarbital is:
- Alkalinizing the urine through systemic absorption
- Binding phenobarbital in the gut and interrupting enterohepatic and enteroenteric circulation
- Directly metabolizing phenobarbital into hydrophilic products
- Stimulating renal excretion by increasing urine flow
Correct Answer: Binding phenobarbital in the gut and interrupting enterohepatic and enteroenteric circulation
Q26. When administering intravenous sodium bicarbonate for urinary alkalinization, which electrolyte should be closely monitored?
- Serum magnesium only
- Serum potassium due to risk of hypokalemia
- Serum ferritin levels
- Serum uric acid exclusively
Correct Answer: Serum potassium due to risk of hypokalemia
Q27. Which statement about hemodialysis for barbiturate removal is correct?
- Hemodialysis is highly effective for ultra‑short acting highly lipid‑soluble barbiturates like thiopental
- Hemodialysis is generally ineffective for phenobarbital due to high protein binding
- Hemodialysis is useful for phenobarbital because it has lower lipid solubility and significant unbound fraction
- Hemodialysis should be avoided because it increases CNS penetration of barbiturates
Correct Answer: Hemodialysis is useful for phenobarbital because it has lower lipid solubility and significant unbound fraction
Q28. In pregnancy, barbiturate exposure is concerning because:
- Barbiturates do not cross the placenta and are therefore harmless
- They cross the placenta and may cause fetal and neonatal respiratory depression or withdrawal
- They selectively damage fetal bone without CNS effects
- They are rapidly metabolized by the placenta making maternal use safe
Correct Answer: They cross the placenta and may cause fetal and neonatal respiratory depression or withdrawal
Q29. Which clinical maneuver helps differentiate opioid from barbiturate overdose at the bedside?
- Administration of naloxone will reverse opioid but not barbiturate-induced respiratory depression
- Pupillary dilation is specific to barbiturates only
- Barbiturates produce hyperthermia while opioids produce hypothermia
- Opioids never cause altered sensorium while barbiturates always do
Correct Answer: Administration of naloxone will reverse opioid but not barbiturate-induced respiratory depression
Q30. The most effective public health strategy to reduce morbidity from prescription barbiturate overdose is:
- Encouraging patients to stock large amounts of barbiturates at home
- Strict prescribing control, patient education on risks, and safe storage/disposal
- Replacing all barbiturates with over-the-counter alternatives
- Discouraging healthcare monitoring to reduce stigma
Correct Answer: Strict prescribing control, patient education on risks, and safe storage/disposal
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