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Pharmacology 3% exam weight

ADR classification (Rawlins-Thompson)

Part of the INI CET (AIIMS PG) study roadmap. Pharmacology topic pharma-010 of Pharmacology.

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ADR classification (Rawlins-Thompson)

🟢 Lite — Quick Review (1h–1d)

Rapid summary for last-minute revision before your INI CET seat.

Pharmacovigilance is the science of detecting, assessing, understanding, and preventing adverse drug reactions (ADRs). An ADR is a noxious, unintended response to a drug at doses normally used in humans; an Adverse Event (AE) is simply any untoward occurrence during treatment, with no causality implied.

ADR classification (Rawlins-Thompson):

TypeNatureDose-related?Example
A – AugmentedPredictable, commonYesBleeding with warfarin
B – BizarreUnpredictable, rareNoPenicillin anaphylaxis
C – ChronicLong-term useYesAdrenal suppression with steroids
D – DelayedLate onsetNoCarcinogenesis
E – End-of-useWithdrawal—Opioid withdrawal
F – FailureTherapeutic failureYesAntibiotic resistance

Naranjo thresholds (memorise): Definite ≥9, Probable 5–8, Possible 1–4, Doubtful ≤0.

🟡 Standard — Regular Study (2d–2mo)

Standard content for building clinical pharmacology reasoning before the exam.

Seriousness Criteria vs Severity

A Serious Adverse Event (SAE) triggers reporting if it causes death, is life-threatening, requires or prolongs hospitalisation, produces persistent disability, causes a congenital anomaly, or is otherwise medically important. Severity (mild/moderate/severe) describes intensity, not seriousness — a mild rash can still be “serious” if it triggers admission.

Causality Assessment Tools

The WHO-UMC scale assigns categories Certain, Probable/Likely, Possible, Unlikely, Conditional/Unclassified, and Unassessable/Unclassifiable based on temporal relation, dechallenge/rechallenge, and confounding. The Naranjo algorithm is a 10-question score sheet used widely for individual cases.

Mnemonic: “C-P-P-U-C-U” for WHO-UMC (Certain, Probable, Possible, Unlikely, Conditional, Unassessable).

PvPI Structure in India

The Pharmacovigilance Programme of India (PvPI) is coordinated by the Indian Pharmacopoeia Commission (IPC), Ghaziabad, acting as the National Coordination Centre (NCC) since 2010. ADR Monitoring Centres (AMCs) operate in medical colleges; reports flow into VigiFlow (the WHO-UMC software) under the WHO Programme for International Drug Monitoring.

Reporting Timelines — High-Yield Trap

  • Healthcare professionals / patients: voluntary reporting through VigiFlow; no fixed statutory deadline.
  • Manufacturers (Marketing Authorisation Holders): 15 calendar days (expedited reporting) for serious + unexpected ADRs under Schedule Y / New Drugs and Clinical Trials Rules (NDCTR) 2019.
  • PSURs (Periodic Safety Update Reports): submitted as per NDCTR 2019 cycles for newly approved drugs.

Common trap: students attribute the 15-day deadline to doctors — it applies to manufacturers only.

🔴 Extended — Deep Study (3mo+)

Comprehensive coverage for candidates targeting top ranks and integrated clinical questions.

Pharmacogenomic ADR Associations (Increasingly Tested)

  • HLA-B*1502 → carbamazepine-induced Stevens-Johnson Syndrome (SJS)/TEN in Han Chinese, Thai, and Indian populations; FDA mandates genotyping before initiation in at-risk groups.
  • HLA-B*5701 → abacavir hypersensitivity; pre-treatment screening is now standard.
  • G6PD deficiency → haemolysis with primaquine, dapsone, sulphonamides, nitrofurantoin.
  • CYP2C9 / VKORC1 polymorphisms → warfarin sensitivity and bleeding risk.
  • Clozapine → agranulocytosis; mandatory WBC monitoring via the Clozapine REMS programme (also tested under antipsychotic safety).

Edge Cases in ADR Classification

  • Type F (Failure of therapy) overlaps with antimicrobial resistance and is a grey zone between pharmacology and microbiology.
  • Withdrawal (Type E) reactions may be mislabelled as new adverse events — e.g., rebound hypertension on stopping clonidine.
  • An “unexpected” ADR is one whose nature, severity, or outcome is not consistent with the Investigator’s Brochure / prescribing information — not merely “rare.”

Common Mistakes in INI CET MCQs

  1. Treating ADR and AE as synonyms — AEs without causal link do not qualify as ADRs.
  2. Misreading Naranjo score boundaries (≥9 vs 5–8 vs 1–4).
  3. Assigning idiosyncratic Type B reactions as preventable.
  4. Forgetting that PSURs (not PSUR-like documents alone) and RMPs (Risk Management Plans) are mandated under NDCTR 2019 for new drugs.

Practice Prompts

  1. A score of 7 on the Naranjo algorithm places the ADR in which category, and what is the next recommended step before labelling it “definite”?
  2. A manufacturer receives a single report of fatal hepatotoxicity with a recently approved oral anticoagulant 22 days after marketing. Under NDCTR 2019, is this reportable as expedited, and by when?

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