Definition and classification of adverse drug reactions (ADRs) MCQs With Answer
Adverse drug reactions (ADRs) are unwanted or harmful effects that occur at normal therapeutic doses. Clear definitions, pharmacological mechanisms, and robust classification systems (e.g., Rawlins & Thompson, WHO) help B. Pharm students identify, predict and manage ADRs. Key concepts include Type A (predictable, dose-related) and Type B (idiosyncratic, non‑dose-related) reactions, immunologic allergies, pharmacokinetic and pharmacodynamic causes, severity versus seriousness, causality assessment (Naranjo, WHO‑UMC) and pharmacovigilance reporting. Understanding preventability, monitoring strategies, and common high‑risk examples prepares future pharmacists for clinical practice and safety surveillance. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What is the most widely accepted definition of an adverse drug reaction (ADR)?
- An unintended therapeutic benefit from a drug
- A harmful or unpleasant reaction occurring at normal therapeutic doses
- A side effect that occurs only in overdose situations
- A reaction occurring only from medication errors
Correct Answer: A harmful or unpleasant reaction occurring at normal therapeutic doses
Q2. Which classification divides ADRs into Type A and Type B?
- Gell and Coombs classification
- Rawlins and Thompson classification
- WHO Essential Medicines List
- Naranjo scale
Correct Answer: Rawlins and Thompson classification
Q3. Which characteristic best describes a Type A ADR?
- Unpredictable and immune‑mediated
- Dose‑related and predictable from pharmacology
- Occurs only after prolonged therapy
- Always fatal
Correct Answer: Dose‑related and predictable from pharmacology
Q4. Which of the following is an example of a Type B ADR?
- Hypoglycemia from insulin overdose
- Gastrointestinal upset from aspirin
- Penicillin‑induced anaphylaxis
- Bradycardia from beta‑blockers at high dose
Correct Answer: Penicillin‑induced anaphylaxis
Q5. The Naranjo algorithm is used to assess:
- Severity of an ADR
- Causality between drug and adverse event
- Pharmacokinetic interactions
- Cost‑effectiveness of therapy
Correct Answer: Causality between drug and adverse event
Q6. Which term describes an adverse event that occurs due to abnormal host response unrelated to drug pharmacology?
- Type A reaction
- Pseudoallergic reaction
- Type B reaction
- Side effect
Correct Answer: Type B reaction
Q7. Which Gell and Coombs type is immediate IgE‑mediated hypersensitivity?
- Type I
- Type II
- Type III
- Type IV
Correct Answer: Type I
Q8. Which ADR classification emphasizes predictability from pharmacokinetics and pharmacodynamics?
- Type B only
- Type A only
- Type C (chronic) only
- Error‑related ADRs
Correct Answer: Type A only
Q9. Which of the following is considered a preventable ADR?
- Idiosyncratic hepatotoxicity with no risk factors
- Allergic rash in a patient with known allergy who is re‑exposed
- Teratogenic effect occurring despite pregnancy testing
- Genetically predisposed enzyme deficiency causing toxicity
Correct Answer: Allergic rash in a patient with known allergy who is re‑exposed
Q10. Which WHO‑UMC causality category indicates a reasonable temporal relationship and unlikely alternative causes?
- Unassessable
- Certain
- Possible
- Unlikely
Correct Answer: Possible
Q11. Which ADR type is described as “time‑related” and often appears after prolonged treatment?
- Type A
- Type B
- Type C
- Type E
Correct Answer: Type C
Q12. Which mechanism commonly explains dose‑related ADRs?
- Immune complex formation
- Pharmacodynamic exaggeration of drug effect
- Autoimmune response
- Hapten formation
Correct Answer: Pharmacodynamic exaggeration of drug effect
Q13. Which adverse reaction term refers to a non‑immune reaction that clinically mimics allergy?
- Idiosyncrasy
- Pseudoallergic reaction
- Type IV hypersensitivity
- Teratogenic effect
Correct Answer: Pseudoallergic reaction
Q14. Which of the following indicates a “serious” ADR by regulatory definition?
- Minor rash resolving spontaneously
- Hospitalization or prolongation of hospitalization
- Transient headache
- Mild nausea
Correct Answer: Hospitalization or prolongation of hospitalization
Q15. Which pharmacokinetic cause can increase ADR risk by raising drug levels?
- Enzyme induction
- Increased renal clearance
- Enzyme inhibition
- Enhanced protein binding
Correct Answer: Enzyme inhibition
Q16. The Yellow Card scheme in pharmacovigilance is primarily associated with which country?
- United States
- India
- United Kingdom
- Australia
Correct Answer: United Kingdom
Q17. Which ADR monitoring method relies on spontaneous voluntary reports from healthcare professionals?
- Active surveillance
- Spontaneous reporting system
- Randomized controlled trials
- Prescription event monitoring only
Correct Answer: Spontaneous reporting system
Q18. Rechallenge that reproduces the adverse effect after stopping and reintroducing the drug provides evidence for what?
- Severity assessment only
- Definitive causality
- No useful information
- Confirms preventability but not causality
Correct Answer: Definitive causality
Q19. Which ADR type is typically associated with withdrawal reactions when a drug is stopped?
- Type D (withdrawal)
- Type A
- Type B
- Type E (withdrawal)
Correct Answer: Type E (withdrawal)
Q20. Which organ is most commonly implicated in serious idiosyncratic ADRs related to drug metabolism?
- Skin
- Liver
- Bone marrow
- Kidney
Correct Answer: Liver
Q21. Which parameter expresses the increase in risk of an ADR in the exposed group relative to unexposed?
- Absolute risk
- Number needed to treat
- Relative risk
- Incidence density only
Correct Answer: Relative risk
Q22. Stevens‑Johnson syndrome is best classified as which type of ADR manifestation?
- Cardiovascular ADR
- Severe cutaneous adverse reaction
- Minor allergic rash
- Gastrointestinal intolerance
Correct Answer: Severe cutaneous adverse reaction
Q23. In pharmacovigilance signal detection, a “signal” means:
- Confirmed causal association
- Evidence suggesting a new causal association or new aspect of a known association
- An adverse event that is always benign
- Only laboratory anomalies
Correct Answer: Evidence suggesting a new causal association or new aspect of a known association
Q24. Which test or approach helps identify whether an ADR is immune‑mediated?
- Therapeutic drug monitoring
- Skin testing or specific IgE measurement
- Electrocardiogram
- Renal function tests
Correct Answer: Skin testing or specific IgE measurement
Q25. Which of the following is NOT typically considered an ADR but rather a medication error?
- Dose omission leading to therapeutic failure
- Anaphylaxis to a drug in an allergic patient
- Heparin‑induced thrombocytopenia
- Drug‑induced liver injury at therapeutic dose
Correct Answer: Dose omission leading to therapeutic failure
Q26. Which preventive strategy reduces ADRs caused by drug–drug interactions?
- Prescribing multiple drugs without review
- Using electronic interaction checking and medication reconciliation
- Avoiding therapeutic drug monitoring
- Ignoring patient comorbidities
Correct Answer: Using electronic interaction checking and medication reconciliation
Q27. A dose‑related extension of a drug’s therapeutic effect (e.g., bleeding with warfarin) is best described as:
- Type B ADR
- Type A ADR
- Allergic reaction
- Idiosyncrasy
Correct Answer: Type A ADR
Q28. Pharmacogenomic testing before prescribing can help prevent which ADRs?
- All ADRs irrespective of mechanism
- Genetically‑predicted idiosyncratic reactions (e.g., HLA‑associated hypersensitivity)
- Allergic reactions without genetic markers
- Medication administration errors
Correct Answer: Genetically‑predicted idiosyncratic reactions (e.g., HLA‑associated hypersensitivity)
Q29. Which regulatory action is issued when an ADR risk requires clinicians to follow special monitoring and warnings?
- Black box warning
- OTC approval
- Patent extension
- Formulary deletion only
Correct Answer: Black box warning
Q30. Which statement best differentiates an adverse event (AE) from an ADR?
- An AE is always caused by the drug; an ADR is unrelated
- An AE is any untoward medical occurrence, while an ADR is a harmful response with at least a reasonable possibility of a causal relationship to the drug
- AEs are always serious, ADRs are always mild
- There is no difference; the terms are interchangeable
Correct Answer: An AE is any untoward medical occurrence, while an ADR is a harmful response with at least a reasonable possibility of a causal relationship to the drug
