Drug allergy MCQs With Answer

Drug allergy MCQs With Answer

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Introduction: Drug allergy MCQs With Answer is a focused resource for B. Pharm students to master drug hypersensitivity, adverse drug reaction (ADR) mechanisms, diagnosis, and management. This concise guide covers key topics such as immunologic types (I–IV), anaphylaxis recognition and treatment, penicillin allergy testing, cross-reactivity, skin tests, drug causality assessment, pharmacovigilance, and desensitization protocols. Emphasis on clinical signs, investigations, prevention, and safe prescribing prepares students for exams and pharmacy practice. These MCQs reinforce critical thinking, case-based application, and evidence-based approaches to drug allergy. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which classification system divides drug hypersensitivity reactions into Types I–IV based on immune mechanisms?

  • Gell and Coombs classification
  • WHO ATC classification
  • Naranjo algorithm
  • Roussel Uclaf Causality Assessment Method

Correct Answer: Gell and Coombs classification

Q2. Which immunologic mechanism is primarily responsible for immediate urticaria and anaphylaxis after drug exposure?

  • Type I hypersensitivity (IgE-mediated)
  • Type II hypersensitivity (cytotoxic)
  • Type III hypersensitivity (immune complex)
  • Type IV hypersensitivity (T-cell mediated)

Correct Answer: Type I hypersensitivity (IgE-mediated)

Q3. What is the first-line drug for emergency treatment of anaphylaxis due to drug allergy?

  • Intramuscular epinephrine
  • Intravenous hydrocortisone
  • Oral antihistamine
  • Subcutaneous epinephrine

Correct Answer: Intramuscular epinephrine

Q4. Which clinical feature is most characteristic of a Type IV (delayed) drug hypersensitivity?

  • Contact dermatitis appearing 48–72 hours after exposure
  • Immediate angioedema within minutes
  • Immune hemolytic anemia within hours
  • Serum sickness-like immune complex deposition in minutes

Correct Answer: Contact dermatitis appearing 48–72 hours after exposure

Q5. A patient reports ‘penicillin allergy’ from childhood. Best step to confirm true allergy in a febrile patient needing a beta-lactam is:

  • Skin testing followed by graded challenge if negative
  • Automatic lifetime avoidance of all beta-lactams
  • Administer full-dose penicillin without testing
  • Give oral antihistamine and proceed

Correct Answer: Skin testing followed by graded challenge if negative

Q6. Cross-reactivity between penicillins and which antibiotic class is clinically most relevant?

  • Cephalosporins
  • Macrolides
  • Fluoroquinolones
  • Aminoglycosides

Correct Answer: Cephalosporins

Q7. Which test is used to detect drug-specific IgE antibodies for immediate hypersensitivity?

  • Serum specific IgE assay (ImmunoCAP)
  • Patch testing
  • Lymphocyte transformation test (LTT)
  • Direct antiglobulin test (Coombs)

Correct Answer: Serum specific IgE assay (ImmunoCAP)

Q8. Fixed drug eruption typically recurs at the same site after re-exposure to the causative drug because of:

  • Resident memory T cells in the skin
  • Circulating IgM antibodies
  • Immune complex deposition only in that site
  • Local bacterial colonization

Correct Answer: Resident memory T cells in the skin

Q9. Which severe cutaneous adverse reaction (SCAR) has the highest mortality and requires immediate drug withdrawal?

  • Toxic epidermal necrolysis (TEN)
  • Urticaria
  • Fixed drug eruption
  • Maculopapular rash

Correct Answer: Toxic epidermal necrolysis (TEN)

Q10. Which HLA allele is strongly associated with carbamazepine-induced Stevens-Johnson syndrome in certain populations?

  • HLA-B*1502
  • HLA-A*0201
  • HLA-DR4
  • HLA-B27

Correct Answer: HLA-B*1502

Q11. In suspected drug-induced immune hemolytic anemia, which laboratory test is most helpful?

  • Direct antiglobulin test (Coombs test)
  • Serum tryptase
  • Patch test
  • Skin prick test

Correct Answer: Direct antiglobulin test (Coombs test)

Q12. Which classification best describes NSAID hypersensitivity with respiratory symptoms like asthma exacerbation?

  • Aspirin-exacerbated respiratory disease (AERD)
  • Immediate IgE-mediated NSAID allergy
  • Type II cytotoxic NSAID reaction
  • Fixed drug eruption

Correct Answer: Aspirin-exacerbated respiratory disease (AERD)

Q13. When assessing causality of a suspected drug allergy, which scale helps estimate likelihood of an adverse drug reaction?

  • Naranjo algorithm
  • Gell and Coombs classification
  • Roussel Uclaf scales for DILI only
  • APACHE II score

Correct Answer: Naranjo algorithm

Q14. The lymphocyte transformation test (LTT) is most useful for diagnosing which type of drug reaction?

  • Type IV delayed hypersensitivity
  • Immediate IgE-mediated anaphylaxis
  • Type II cytotoxic reactions
  • Type III immune complex reactions

Correct Answer: Type IV delayed hypersensitivity

Q15. Which management step is most appropriate after recognizing a drug-induced anaphylactic shock?

  • Administer intramuscular epinephrine immediately and call emergency support
  • Wait for laboratory confirmation before treatment
  • Only give intravenous antibiotics
  • Place patient supine without airway management

Correct Answer: Administer intramuscular epinephrine immediately and call emergency support

Q16. For patients with confirmed IgE-mediated allergy to a chemotherapy agent with no alternatives, the recommended approach is:

  • Drug desensitization under specialist supervision
  • Permanent avoidance with no further action
  • Switch to same-class drug without testing
  • Use of oral antihistamine alone during infusion

Correct Answer: Drug desensitization under specialist supervision

Q17. Which adverse reaction pattern is most suggestive of a Type III (immune complex) drug hypersensitivity?

  • Serum sickness–like syndrome with fever, arthralgia, and rash
  • Immediate urticaria and bronchospasm
  • Isolated contact dermatitis
  • IgG-mediated hemolysis

Correct Answer: Serum sickness–like syndrome with fever, arthralgia, and rash

Q18. Which is the most reliable method to de-label a patient with a history of non-severe penicillin allergy?

  • Direct oral or IV graded drug challenge after negative skin test when indicated
  • Lifetime avoidance without testing
  • Routine patch testing only
  • Empiric desensitization in all cases

Correct Answer: Direct oral or IV graded drug challenge after negative skin test when indicated

Q19. Which monitoring parameter is useful immediately after treating anaphylaxis to detect biphasic reactions?

  • Observation for at least 4–6 hours with vital signs monitoring
  • Discharge as soon as respiratory symptoms resolve
  • No need for observation if epinephrine was given
  • Only check serum IgE levels

Correct Answer: Observation for at least 4–6 hours with vital signs monitoring

Q20. Patch testing is primarily indicated for diagnosing which type of drug allergy?

  • Delayed contact-type reactions (Type IV)
  • Immediate anaphylactic reactions
  • Drug-induced hemolysis
  • Type III serum sickness

Correct Answer: Delayed contact-type reactions (Type IV)

Q21. Which biomarker can be elevated in the blood shortly after an anaphylactic event and supports the diagnosis?

  • Serum tryptase
  • C-reactive protein
  • Serum creatinine
  • Alanine aminotransferase

Correct Answer: Serum tryptase

Q22. Which antibiotic is most commonly implicated in IgE-mediated anaphylaxis worldwide?

  • Penicillins
  • Tetracyclines
  • Glycopeptides
  • Fusidic acid

Correct Answer: Penicillins

Q23. Which principle is important when counseling patients labeled with a severe cutaneous adverse reaction (SCAR)?

  • Strict and permanent avoidance of the implicated drug and clear documentation
  • Advise re-exposure if symptoms were mild
  • Encourage self-challenge at home to reconfirm
  • Use alternative OTC medications without consultation

Correct Answer: Strict and permanent avoidance of the implicated drug and clear documentation

Q24. A maculopapular rash developing 7–10 days after starting allopurinol suggests which mechanism?

  • Delayed T-cell mediated hypersensitivity often linked to HLA risk alleles
  • Immediate IgE-mediated reaction
  • IgM-mediated cytotoxicity
  • Non-immune dose-related toxicity

Correct Answer: Delayed T-cell mediated hypersensitivity often linked to HLA risk alleles

Q25. Which strategy reduces the incidence of drug allergies from contrast media in high-risk patients?

  • Pre-medication with corticosteroids and antihistamines when indicated
  • Routine avoidance of imaging studies
  • Use of nephrotoxic agents concomitantly
  • Administering full-dose contrast without precautions

Correct Answer: Pre-medication with corticosteroids and antihistamines when indicated

Q26. Which adverse reaction is characteristic of a Type II (cytotoxic) drug hypersensitivity?

  • Drug-induced immune thrombocytopenia
  • Delayed maculopapular rash only
  • Immediate urticaria alone
  • Serum sickness-like illness

Correct Answer: Drug-induced immune thrombocytopenia

Q27. For pharmacovigilance of suspected drug allergies, pharmacists should do which of the following?

  • Report suspected cases to national ADR reporting systems and document in patient records
  • Never report unless confirmed by a specialist
  • Only report when a fatality occurs
  • Advise patients to ignore mild rashes

Correct Answer: Report suspected cases to national ADR reporting systems and document in patient records

Q28. In a patient with multiple drug allergies, which investigation can help identify the culprit in delayed reactions?

  • Drug patch testing and lymphocyte transformation test
  • Immediate skin prick test only
  • Serum creatinine measurement
  • Urine culture

Correct Answer: Drug patch testing and lymphocyte transformation test

Q29. Which statement about desensitization protocols is correct?

  • Desensitization induces temporary tolerance and must be repeated if the drug is stopped
  • Desensitization provides permanent immune tolerance
  • It is safe to perform desensitization without monitoring
  • Desensitization is contraindicated for all IgE-mediated reactions

Correct Answer: Desensitization induces temporary tolerance and must be repeated if the drug is stopped

Q30. Which factor increases the risk of severe cutaneous adverse reactions (SCARs) to certain drugs?

  • Presence of specific HLA risk alleles and prior viral infection
  • Low body weight only
  • Short duration of drug exposure always protective
  • Mild seasonal allergies

Correct Answer: Presence of specific HLA risk alleles and prior viral infection

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