Clinically Important Interactions
Identify the listed prescription most likely to interact with a named medicine and cause the stated clinical problem.
How to prepare for the PSA
Combine patient-centred prescribing judgement with fast BNF navigation, reliable calculations, complete prescriptions and explicit monitoring and communication.
Core concepts
Concept 1
An ADR interaction item names one medicine and asks which current prescription is most likely to interact and produce a defined consequence.
Exam cue: Use the stated clinical consequence to narrow the interaction search.
Concept 2
The important answer is the interaction with the strongest relevance to the patient's presentation, not every pair listed in a database.
Exam cue: Check both medicines, direction of effect and patient susceptibility.
Concept 3
Pharmacodynamic and pharmacokinetic interactions may increase toxicity, reduce effectiveness or require dose, timing or monitoring changes.
Exam cue: Distinguish a manageable interaction from one that makes the combination inappropriate.
Risk pitfalls and guardrails
Choosing a theoretical interaction unrelated to the stated problem.
Guardrail: Do not let a familiar medicine, reference search or calculator output replace patient-specific safety checks and escalation.
Selecting the medicine already named in the lead-in instead of its interacting partner.
Guardrail: Do not let a familiar medicine, reference search or calculator output replace patient-specific safety checks and escalation.
Assuming every interaction requires the same response.
Guardrail: Do not let a familiar medicine, reference search or calculator output replace patient-specific safety checks and escalation.
Memory anchors
Named Medicine
Start with the medicine specified in the lead-in.
Interacting Partner
Select the current prescription that produces the stated clinical consequence.
Direction of Effect
Decide whether exposure, effect or toxicity is increased or reduced.
Patient Susceptibility
Organ function, age and comorbidity can magnify interaction harm.
Proportionate Response
The interaction may require avoidance, adjustment, monitoring or advice.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
Which combination most increases serotonin-syndrome risk?
Which combination most increases hyperkalaemia risk?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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