14.1 Adverse Drug Reactions & Reporting
Key Takeaways
- Type A (augmented) ADRs are dose-related and predictable from pharmacology; Type B (bizarre) ADRs are idiosyncratic, less dose-predictable, and include true hypersensitivity
- Serious ADRs include death, life-threatening events, hospitalisation or prolongation, disability, congenital anomaly, and other medically important events needing intervention
- Australian pharmacists report suspected adverse events to the TGA (Blue Card / online systems); quality reports need drug, reaction, timing, outcome, and relevant history
- Distinguish expected, manageable side effects from unexpected or serious reactions that require action, documentation, and often reporting
- Dechallenge (improvement after stopping) and careful rechallenge concepts support causality assessment—but rechallenge is rarely appropriate after serious reactions
13.1 Adverse Drug Reactions & Reporting
Quick Answer: Under Standard 3.3, pharmacists must detect, assess, manage, document, and report adverse drug reactions (ADRs). Classify reactions as Type A (dose-related, pharmacology-predictable) or Type B (idiosyncratic/hypersensitivity), judge seriousness, counsel patients on expected versus urgent symptoms, and submit quality TGA adverse event reports when indicated. Causality is supported by timing, dechallenge, and—only when clinically justified—rechallenge; never rechallenge after life-threatening hypersensitivity without specialist oversight.
Monitoring is incomplete if you only check blood pressure and INR. Safety monitoring means noticing harm that medicines may cause, deciding whether the reaction is expected or serious, protecting the patient, and feeding the national pharmacovigilance system so future patients benefit.
What counts as an adverse drug reaction
An adverse drug reaction is a noxious and unintended response to a medicine used at doses normally used for prophylaxis, diagnosis, or therapy (or for modification of physiological function). Related terms:
| Term | Practical meaning for the intern exam |
|---|---|
| Side effect | Often used for expected, pharmacology-related effects that may be tolerable or dose-manageable |
| Adverse event | Any untoward medical occurrence during treatment; may or may not be caused by the drug |
| Adverse drug reaction (ADR) | Adverse event with a reasonable possibility of drug causality |
| Medication error / harm | Wrong drug, dose, patient, or route; may cause ADR-like harm but root cause is process failure |
On exam scenarios, focus on clinical recognition and next steps, not philosophical definitions. Ask: Is this likely drug-related? Is it serious? What do I stop, treat, document, report, and counsel?
Type A versus Type B ADRs
A durable classification still used in teaching and practice:
Type A — “augmented”
- Predictable from known pharmacology
- Usually dose-related
- Commoner; often reversible with dose reduction or cessation
- Examples: ACE inhibitor cough (bradykinin-related), NSAID peptic ulcer risk, opioid constipation, benzodiazepine sedation, hypoglycaemia from insulin or sulfonylureas, bleeding from anticoagulants, digoxin toxicity when clearance falls
Management often includes dose adjustment, formulation change, timing change, add-on protective therapy, or switch within class—after weighing benefit.
Type B — “bizarre” / idiosyncratic
- Not readily predicted from primary pharmacology in the usual dose–response sense
- Includes hypersensitivity (IgE-mediated anaphylaxis, severe cutaneous adverse reactions), many idiosyncratic hepatitides, and some blood dyscrasias
- Often rarer, may be more severe, and frequently require permanent avoidance of the culprit and related agents
- Examples: penicillin anaphylaxis, Stevens–Johnson syndrome / toxic epidermal necrolysis (e.g. with some anticonvulsants or allopurinol in susceptible patients), drug reaction with eosinophilia and systemic symptoms (DRESS), clozapine agranulocytosis (immune/idiosyncratic risk profile)
Exam tip: Type A problems invite titration and mitigation; Type B serious hypersensitivity invites stop, treat, document allergy, avoid re-exposure, report when serious/unexpected, and refer when needed.
Other historical labels (Type C chronic, Type D delayed, Type E end-of-use) appear in textbooks; for APC-level reasoning, A vs B plus seriousness and action is the high-yield core.
Seriousness criteria
An ADR is generally considered serious if it results in or prolongs any of the following (international pharmacovigilance-aligned concepts used by regulators including the TGA):
- Death
- Life-threatening event (e.g. anaphylaxis with airway compromise, severe hyperkalaemia with arrhythmia risk)
- Hospitalisation or prolongation of existing hospitalisation
- Persistent or significant disability / incapacity
- Congenital anomaly / birth defect
- Other medically important event requiring intervention to prevent one of the above (e.g. severe neutropenia managed urgently as outpatient but clearly high-risk)
Serious ≠ severe intensity alone. A “severe” headache can be non-serious for reporting priority if self-limiting and expected; mild-feeling early mucocutaneous signs of a serious cutaneous reaction can still be medically important. Always judge medical importance and outcome, not only the patient’s pain score language.
Non-serious but clinically relevant reactions still matter: they drive adherence failure, switches, and quality use of medicines. Document them even if you do not always submit a formal report.
TGA reporting principles for pharmacists (Blue Card / adverse event reporting)
Australia’s medicines regulator is the Therapeutic Goods Administration (TGA). Pharmacists, other health professionals, sponsors, and consumers can report suspected adverse events. You do not need absolute proof of causality—suspicion is enough to report.
Blue Card historically referred to the yellow/blue card-style spontaneous reporting pathway; contemporary practice uses TGA online reporting (and related channels), but exam language may still say “Blue Card” for the national spontaneous ADR reporting concept. Know the principles, not a marketing name:
When reporting is especially important
- Serious ADRs
- Unexpected reactions (not consistent with known product information / common knowledge of the medicine)
- Reactions to new medicines, vaccines, or recently extended indications
- Medication error associated with harm (as appropriate to safety systems)
- Clusters or unusual patterns in your practice
- Reactions involving pregnancy, children, or other under-represented groups when relevant
Expected, mild, well-labelled effects (e.g. transient nausea starting metformin, managed and expected) may not always warrant a formal TGA report, but they still need patient counselling and local documentation if they affect care.
What to document and include in a quality report
Aim for a report that another clinician could reconstruct:
- Patient identifiers appropriate to the system (age, sex; follow privacy rules)
- Suspect medicine(s): name, dose, route, dates started/stopped, indication
- Concomitant medicines and relevant complementary products
- Description of the reaction: signs, symptoms, severity, seriousness, date of onset
- Time course relative to drug start, dose change, or rechallenge
- Outcome: recovered, recovering, not recovered, fatal, unknown; treatments given (e.g. adrenaline, steroids, hospital care)
- Relevant medical history, allergies, renal/hepatic impairment, pregnancy
- Dechallenge / rechallenge information if available
- Reporter contact details for follow-up
Incomplete reports still have value—do not delay a serious report waiting for every lab result—but complete what you can.
Local systems alongside TGA
Hospital pharmacists also use institutional incident and ADR systems, allergy modules in electronic records, and pharmacy software flags. Community pharmacists document in the dispensing record / clinical notes, communicate with the prescriber, and update My Health Record or shared care notes when that is part of workflow and consent rules. TGA reporting does not replace clinical communication with the treating team.
Distinguishing expected side effects from unexpected serious reactions
Use a practical filter at the counter or on the ward:
| Feature | Often “expected side effect” management | Escalate as possible serious/unexpected ADR |
|---|---|---|
| Consistency with known pharmacology | High (e.g. opioid constipation) | Low or idiosyncratic pattern |
| Dose relationship | Improves with lower dose / time | Occurs at any dose; progressive systemic features |
| Red flags | Mild, self-limiting, no organ threat | Anaphylaxis features, severe rash with mucosal involvement, jaundice, unexplained fever + rash + lymphadenopathy, severe cytopenias, acute kidney injury, suicidal crisis |
| Action | Counsel, mitigate, review adherence/benefit | Urgent assessment/ED if needed, stop culprit when safe, document, notify prescriber, report |
Examples for exam scenarios:
- Dry cough weeks after starting an ACE inhibitor → classic Type A; discuss switch to ARB with prescriber; usually not an “allergy” label for all renin–angiotensin drugs without care
- Generalised urticaria and dyspnoea 20 minutes after amoxicillin → treat as acute hypersensitivity emergency pathway; document allergy; report if criteria met; never casual rechallenge
- Mild transient nausea day 1 of a new antibiotic → counsel, take with food if appropriate, review if worsens—usually not serious reporting priority
- Blistering rash and oral ulcers after a new anticonvulsant → stop and urgent medical review; potential severe cutaneous ADR
Counselling patients on reporting and self-monitoring
Patient engagement is part of safety monitoring:
- Explain common expected effects and self-care (e.g. loperamide caution with opioids’ constipation strategy; when to take with food).
- Give clear red-flag instructions: when to seek GP same day vs emergency care (swelling of tongue/throat, difficulty breathing, severe rash, black stools, chest pain, severe dizziness, unexplained bruising, fever with severe sore throat on certain agents such as clozapine or carbimazole risk pathways).
- Encourage patients to tell any health professional about past reactions—what drug, what happened, how soon, and what treatment was needed.
- Mention that consumers can also report to the TGA, and that reports improve medicine safety nationally.
- Avoid alarming language that destroys adherence for low-risk, expected effects; balance honesty with context.
Causality: timing, dechallenge, and rechallenge (handle carefully)
Causality is rarely certain from one encounter. Supportive features include:
- Temporal association: reaction after starting or increasing the drug, within a plausible window (minutes for IgE anaphylaxis; days–weeks for many delayed hypersensitivities; variable for Type A)
- Biological plausibility: known ADR profile or class effect
- Exclusion of alternatives: infection, disease flare, other drugs
- Dechallenge: improvement after dose reduction or cessation supports causality (with caveats—some reactions progress despite stopping)
- Rechallenge: recurrence on re-exposure is strong evidence—but deliberate rechallenge after serious Type B reactions is dangerous and generally reserved for specialist settings (e.g. allergy/immunology protocols) when benefit is exceptional
Intern-safe rule: Use dechallenge history in assessment and documentation. Do not recommend casual home rechallenge after anaphylaxis, severe cutaneous reactions, drug-induced liver injury with jaundice, or agranulocytosis. For ambiguous mild Type A effects, planned supervised rechallenge or graded reintroduction may be a prescriber/specialist decision, not a pharmacy-counter experiment.
Putting it together for Standard 3.3
A defensible safety-monitoring response in exam vignettes usually includes:
- Recognise the presentation as possible ADR and classify seriousness urgently
- Protect the patient (first aid/ED pathway, withhold further doses when appropriate)
- Assess culprit(s), timing, concomitant drugs, and Type A vs B pattern
- Communicate with the patient and prescriber; update allergy/ADR records accurately
- Report serious or unexpected events to the TGA with quality detail
- Plan future avoidance, alternatives, and monitoring
Safety reporting is not bureaucracy bolted onto clinical care—it is how individual monitoring becomes system-level learning while you still treat the person in front of you.
Which statement best describes a Type A adverse drug reaction?
A patient develops facial swelling, wheeze, and hypotension within minutes of a dose of parenteral antibiotic in a clinic. After emergency management, which feature most strongly supports classifying the event as a serious ADR for pharmacovigilance purposes?
When submitting a TGA adverse event report for a suspected serious reaction, which approach best matches good reporting practice?
A patient had clear improvement of a pruritic maculopapular rash after a medicine was stopped (positive dechallenge). The original reaction was not anaphylaxis. Which statement about rechallenge is most appropriate for intern-level practice?