Poison & Antidote: Activated charcoal MCQs With Answer

Poison & Antidote: Activated charcoal MCQs With Answer is an essential study set for B.Pharm students focused on the pharmacology and toxicology of activated charcoal. This introduction covers activated charcoal’s mechanism of adsorption, clinical indications for gastrointestinal decontamination, dosing strategies (single and multiple-dose activated charcoal, MDAC), limitations, and common contraindications. Key terms include activated charcoal, adsorption, overdose management, enterohepatic circulation, gastrointestinal decontamination, and toxicokinetics. Designed to deepen understanding for examinations and clinical practice, these MCQs emphasize evidence-based use, drug-specific efficacy, and patient safety considerations. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the primary mechanism by which activated charcoal reduces systemic absorption of poisons?

• Ion exchange
• Covalent binding
• Adsorption to its porous surface
• Chelation of toxins

Correct Answer: Adsorption to its porous surface

Q2. Which of the following is the most accurate statement about activated charcoal and alcohols like ethanol and methanol?

• Activated charcoal effectively adsorbs ethanol and methanol
• Activated charcoal enhances alcohol metabolism in the liver
• Activated charcoal has minimal adsorption of small polar alcohols
• Activated charcoal chelates alcohols reducing toxicity

Correct Answer: Activated charcoal has minimal adsorption of small polar alcohols

Q3. For an adult acute overdose, what is a commonly recommended single-dose adult dose of activated charcoal?

• 5 grams
• 10–25 grams
• 50–100 grams
• 200–300 grams

Correct Answer: 50–100 grams

Q4. Which of the following poisons is least likely to be effectively adsorbed by activated charcoal?

• Carbamazepine
• Theophylline
• Lithium
• Aspirin (salicylate)

Correct Answer: Lithium

Q5. Multiple-dose activated charcoal (MDAC) is particularly indicated for which pharmacokinetic property?

• High renal clearance
• Low bioavailability
• Significant enterohepatic or enteroenteric circulation
• Rapid absorption within 5 minutes

Correct Answer: Significant enterohepatic or enteroenteric circulation

Q6. What is the main reason to avoid activated charcoal in patients with an unprotected airway?

• Charcoal neutralizes anesthetic drugs
• High risk of aspiration leading to chemical pneumonitis
• Charcoal causes airway constriction
• It reduces oxygen delivery

Correct Answer: High risk of aspiration leading to chemical pneumonitis

Q7. Which caustic ingestion scenario is activated charcoal generally NOT recommended?

• Strong acid or alkali ingestion with corrosion risk
• Ingestion of controlled-release tablets
• Ingestion of carbamazepine tablets
• Ingestion of immediate-release antidepressants

Correct Answer: Strong acid or alkali ingestion with corrosion risk

Q8. How does activated charcoal affect the half-life of drugs when MDAC is used?

• It always increases the half-life
• It may decrease plasma half-life by interrupting enterohepatic recirculation
• It converts first-order to zero-order kinetics
• It has no effect on half-life

Correct Answer: It may decrease plasma half-life by interrupting enterohepatic recirculation

Q9. Which of the following preparations is a common formulation of activated charcoal used in emergency departments?

• Intravenous activated charcoal solution
• Charcoal powder in alcoholic solvent
• Oral suspension of activated charcoal in water
• Rectal activated charcoal suppository

Correct Answer: Oral suspension of activated charcoal in water

Q10. Which statement best describes activated charcoal’s adsorption process?

• It chemically reacts and degrades toxins
• It physically adsorbs molecules to its large internal surface area through intermolecular forces
• It forms ionic complexes that neutralize drugs
• It enhances renal elimination by increasing urinary pH

Correct Answer: It physically adsorbs molecules to its large internal surface area through intermolecular forces

Q11. In which of the following overdoses is MDAC most commonly recommended?

• Acute ethanol overdose
• Theophylline overdose
• Lithium overdose
• Iron overdose

Correct Answer: Theophylline overdose

Q12. What is the recommended pediatric single-dose activated charcoal dose (approximate)?

• 0.1 g/kg
• 0.5 g/kg
• 1 g/kg
• 5 g/kg

Correct Answer: 1 g/kg

Q13. Which of the following metals is significantly adsorbed by activated charcoal?

• Iron
• Lead
• Mercury (elemental)
• Most inorganic metals are poorly adsorbed

Correct Answer: Most inorganic metals are poorly adsorbed

Q14. Which factor most reduces the efficacy of activated charcoal administered after an overdose?

• Administration within 15 minutes
• Delay beyond 1–2 hours after ingestion for most drugs
• Use in sustained-release formulations
• Simultaneous administration with MDAC

Correct Answer: Delay beyond 1–2 hours after ingestion for most drugs

Q15. Activated charcoal is often combined with which cathartic historically, though now used less frequently?

• Sorbitol
• Magnesium sulfate IV
• Loperamide
• Calcium carbonate

Correct Answer: Sorbitol

Q16. Which drug property predicts good adsorption to activated charcoal?

• Small molecular weight and high polarity
• Large molecular weight and high lipophilicity
• High water solubility
• Complete ionization at physiological pH

Correct Answer: Large molecular weight and high lipophilicity

Q17. For which of the following is whole bowel irrigation preferred over activated charcoal?

• Most immediate-release tablets
• Lithium or extended-release/enteric-coated tablets visible on X-ray
• Small-molecule alcohol poisoning
• Tricyclic antidepressant immediate-release overdose

Correct Answer: Lithium or extended-release/enteric-coated tablets visible on X-ray

Q18. Which adverse effect is most commonly associated with orally administered activated charcoal?

• Renal failure
• Vomiting
• Severe hypotension
• Pulmonary embolism

Correct Answer: Vomiting

Q19. Activated charcoal is least useful for which class of substances?

• Antidepressants
• Inorganic salts like sodium chloride
• Cardiac glycosides
• Barbiturates

Correct Answer: Inorganic salts like sodium chloride

Q20. What is the role of activated charcoal in enterohepatic recirculation?

• It enhances hepatic metabolism of toxins
• It adsorbs toxins excreted into the gut, interrupting reabsorption
• It increases biliary excretion
• It neutralizes bile acids to reduce toxicity

Correct Answer: It adsorbs toxins excreted into the gut, interrupting reabsorption

Q21. Which of the following is an absolute contraindication to activated charcoal?

• Ingestion of a large amount of paracetamol
• Unprotected airway without endotracheal tube
• Recent gastric lavage
• Hypersalivation

Correct Answer: Unprotected airway without endotracheal tube

Q22. How does particle size and porosity of activated charcoal affect its adsorption capacity?

• Smaller particle size and higher porosity increase surface area and adsorption
• Larger particles have greater adsorption due to mass
• Porosity has no effect on adsorption
• Less porous charcoal adsorbs more toxin

Correct Answer: Smaller particle size and higher porosity increase surface area and adsorption

Q23. Which of the following drugs with enterohepatic cycling is likely to benefit from MDAC?

• Metformin
• Carbamazepine
• Zinc salts
• Isopropyl alcohol

Correct Answer: Carbamazepine

Q24. What is the primary physicochemical interaction responsible for adsorption of organic molecules to activated charcoal?

• Hydrogen bonding exclusively
• Covalent bond formation
• Hydrophobic interactions and van der Waals forces
• Electrostatic ionic bonding

Correct Answer: Hydrophobic interactions and van der Waals forces

Q25. When combined with sorbitol, what was the historically intended benefit of adding sorbitol to activated charcoal?

• Enhance systemic absorption of charcoal
• Act as a cathartic to speed gastrointestinal transit
• Neutralize the poison chemically
• Prevent charcoal from sticking to the mucosa

Correct Answer: Act as a cathartic to speed gastrointestinal transit

Q26. Which of the following is true regarding activated charcoal and oral iron poisoning?

• Activated charcoal reliably adsorbs iron and is first-line
• Activated charcoal poorly adsorbs iron; chelation and decontamination other methods used
• Activated charcoal converts iron to an insoluble form
• Repeated-dose charcoal is standard for iron

Correct Answer: Activated charcoal poorly adsorbs iron; chelation and decontamination other methods used

Q27. In which scenario might activated charcoal be effective even if given several hours after ingestion?

• Immediate-release small-molecule ingestion
• Sustained-release or prolonged-release drug overdose
• Pure ethanol ingestion
• Ingestion of strong acids

Correct Answer: Sustained-release or prolonged-release drug overdose

Q28. Which statement best describes the use of activated charcoal during endoscopy for caustic ingestion?

• Activated charcoal is routinely given before endoscopy
• Activated charcoal is contraindicated in caustic ingestion and endoscopy evaluation
• It improves visualization during endoscopy
• It neutralizes caustic agents allowing safer endoscopy

Correct Answer: Activated charcoal is contraindicated in caustic ingestion and endoscopy evaluation

Q29. What laboratory or imaging finding might prompt consideration of whole bowel irrigation instead of activated charcoal?

• Evidence of tablets visible on abdominal X-ray
• Normal abdominal X-ray with rapid transit
• Low serum potassium
• Elevated liver enzymes

Correct Answer: Evidence of tablets visible on abdominal X-ray

Q30. Which of the following is an important practical step when administering activated charcoal to a conscious patient?

• Ensure the patient has a protected airway and can swallow
• Administer intravenously for faster effect
• Mix with alcohol to increase palatability
• Give only after inducing emesis

Correct Answer: Ensure the patient has a protected airway and can swallow

Q31. Which toxin is classically well adsorbed by activated charcoal?

• Ethylene glycol
• Organophosphates (most types)
• Activated charcoal shows variable adsorption for organophosphates and is often limited
• Inorganic cyanide salts

Correct Answer: Activated charcoal shows variable adsorption for organophosphates and is often limited

Q32. How should activated charcoal be stored in a pharmacy to maintain efficacy?

• In open containers exposed to air and moisture
• In airtight containers away from moisture and contaminants
• Mixed with sorbitol in storage
• Frozen at -20°C

Correct Answer: In airtight containers away from moisture and contaminants

Q33. What is a major limitation of activated charcoal use in mass poisoning incidents?

• Unlimited supply and easy administration
• Logistical challenges, dosing variability, and airway protection requirements
• It is effective for all poisons
• No monitoring is required after administration

Correct Answer: Logistical challenges, dosing variability, and airway protection requirements

Q34. Which of the following is true regarding charcoal and sustained-release theophylline overdose?

• Single-dose charcoal is always sufficient
• MDAC can decrease serum theophylline concentrations and is often recommended
• Charcoal increases the absorption of theophylline
• Theophylline is not adsorbed by charcoal

Correct Answer: MDAC can decrease serum theophylline concentrations and is often recommended

Q35. Which property of activated charcoal makes it effective across a wide range of organic toxins?

• Specific enzyme content
• Very large internal surface area and heterogeneous adsorption sites
• Ability to be absorbed systemically
• pH-dependent chemical reactivity

Correct Answer: Very large internal surface area and heterogeneous adsorption sites

Q36. Which of the following statements about activated charcoal and gastric lavage is most accurate?

• Gastric lavage should always be performed before charcoal
• Gastric lavage may be considered if within one hour of a life-threatening ingestion and if airway protected; charcoal may follow lavage
• Gastric lavage and charcoal are contraindicated together
• Charcoal must be given prior to any lavage to be effective

Correct Answer: Gastric lavage may be considered if within one hour of a life-threatening ingestion and if airway protected; charcoal may follow lavage

Q37. What is the effect of activated charcoal on drug bioavailability when given immediately after ingestion?

• It can significantly reduce bioavailability by adsorbing the drug in the gut
• It increases bioavailability by facilitating absorption
• It has no effect on bioavailability
• It enzymatically degrades the drug

Correct Answer: It can significantly reduce bioavailability by adsorbing the drug in the gut

Q38. Which clinical sign after charcoal administration would be most concerning for aspiration?

• Improved oxygen saturation
• Development of cough, hypoxia, and new infiltrate on chest X-ray
• Normal breath sounds
• Increased urine output

Correct Answer: Development of cough, hypoxia, and new infiltrate on chest X-ray

Q39. Why is activated charcoal not effective for cyanide poisoning?

• Cyanide is strongly adsorbed, so charcoal is too toxic
• Cyanide is rapidly absorbed and small, highly water-soluble, and not well adsorbed by charcoal
• Charcoal chemically converts cyanide to thiocyanate
• Charcoal causes release of cyanide from complexes

Correct Answer: Cyanide is rapidly absorbed and small, highly water-soluble, and not well adsorbed by charcoal

Q40. For how long after ingestion is single-dose activated charcoal usually considered most effective for immediate-release drugs?

• Within 24 hours
• Within 1–2 hours
• Only after 6 hours
• Only if given before ingestion

Correct Answer: Within 1–2 hours

Q41. Which feature distinguishes adsorption from absorption in the context of activated charcoal?

• Adsorption involves uptake into the bulk phase of charcoal
• Adsorption is surface binding of molecules; absorption is uptake into volume
• They are identical processes
• Absorption occurs only with gases

Correct Answer: Adsorption is surface binding of molecules; absorption is uptake into volume

Q42. Which drug is a classic example where activated charcoal is not useful due to poor adsorption?

• Carbamazepine
• Iron salts
• Phenobarbital
• Dapsone

Correct Answer: Iron salts

Q43. When administering activated charcoal via nasogastric tube, which precaution is most important?

• Use in all patients regardless of airway status
• Ensure correct tube placement and airway protection to prevent aspiration
• Always mix with oral chelators
• Give only after patient vomits

Correct Answer: Ensure correct tube placement and airway protection to prevent aspiration

Q44. In which poisoning is activated charcoal combined with MDAC specifically recommended by many guidelines?

• Acute methanol poisoning
• Dapsone poisoning
• Acute iron overdose
• Severe hypoglycemia

Correct Answer: Dapsone poisoning

Q45. What is a potential gastrointestinal complication of massive activated charcoal administration?

• Gastrointestinal bleeding due to anticoagulation
• Bowel obstruction or impaction
• Peptic ulcer formation
• Increased intestinal absorption of toxins

Correct Answer: Bowel obstruction or impaction

Q46. How does activated charcoal interact with oral activated charcoal-coated drugs?

• It may further adsorb the drug, reducing absorption
• It dissolves the coating and increases absorption
• It has no interaction with coated tablets
• It enhances coating adherence

Correct Answer: It may further adsorb the drug, reducing absorption

Q47. Which of the following is a pharmacokinetic rationale for using activated charcoal in overdose of drugs with large volume of distribution?

• Charcoal increases volume of distribution
• Charcoal may still reduce absorption or interrupt enterohepatic recirculation even if Vd is large
• Large Vd drugs are always effectively removed by charcoal
• Charcoal converts drug to hydrophilic metabolites

Correct Answer: Charcoal may still reduce absorption or interrupt enterohepatic recirculation even if Vd is large

Q48. Which of the following operational factors can reduce the adsorption capacity of activated charcoal?

• Fresh charcoal stored in airtight containers
• Prolonged exposure to moisture and volatile contaminants
• Proper reconstitution immediately before use
• Using recommended dosing regimens

Correct Answer: Prolonged exposure to moisture and volatile contaminants

Q49. Which statement best describes the evidence basis for routine use of activated charcoal in all poisonings?

• There is strong evidence supporting routine use in all cases
• Use should be individualized based on toxin, timing, airway status, and risks; not routine for all poisonings
• Charcoal is never useful and should be abandoned
• It should only be used in pediatric patients

Correct Answer: Use should be individualized based on toxin, timing, airway status, and risks; not routine for all poisonings

Q50. Which of the following best summarizes a safe clinical approach to activated charcoal administration?

• Administer to every patient with suspected ingestion without assessment
• Assess airway protection, time since ingestion, substance characteristics, and potential benefit versus risk before administration
• Prefer gastric lavage over charcoal in all cases
• Give charcoal only after 24 hours to ensure patient stability

Correct Answer: Assess airway protection, time since ingestion, substance characteristics, and potential benefit versus risk before administration