The PSA
Section 7 of 8
Drug monitoring
Choose the right way and timing to monitor the benefit and harm of therapy.
16 marks · 8% of the exam8 items × 2
What it tests
Which test, and when, to monitor a drug’s efficacy and safety. Memorise the monitoring for the high-risk drugs.
How to tackle it
- 1Ask: what is the key efficacy measure and the key safety/toxicity measure for this drug?
- 2Note the correct timing (e.g. lithium level 12 h post-dose; INR frequency after starting warfarin)
Worked example
A patient with AF is established on warfarin.
Answer
Monitor the INR (target 2.0–3.0 for AF/VTE), more frequently after dose changes.
Pitfalls & high-yield
- Know these monitoring pairs: warfarin→INR; digoxin→levels + K⁺; lithium→levels (12 h) + U&E/TFT; DMARDs (methotrexate)→FBC/LFT/U&E; statins→LFT/CK; amiodarone→TFT/LFT/CXR; aminoglycosides→levels + renal function.
- Timing matters — a level taken at the wrong time is uninterpretable.
Prep
How it’s marked
2 marks per item, 8 items = 16 of 200 marks. Standard-set per sitting (pass mark ≈ 60–63%, varies).