Patient safety and safe prescribing
What the exam asks
Safe prescribing questions test dose calculation, high-risk drugs, interactions and the systems that prevent harm. Nearly every vignette contains a deliberate prescribing error to spot.
Core rules
- Prescribe completely and legally: name, date of birth, weight in children, dose in mg and volume, route, frequency and indication.
- High-risk medicines: insulin, anticoagulants, opioids, methotrexate, digoxin and potassium. Insulin and methotrexate are the classic wrong-route and wrong-frequency errors.
- Check renal function: dose-reduce or avoid in AKI; use Cockcroft-Gault creatinine clearance for DOACs, and remember DOACs are contraindicated in mechanical heart valves.
- Interactions to memorise: ACE inhibitor plus NSAID plus diuretic (the 'triple whammy') causes AKI; SSRIs with triptans or tramadol cause serotonin syndrome; warfarin with most antibiotics raises the INR.
- Reversal: warfarin - vitamin K plus prothrombin complex concentrate; dabigatran - idarucizumab; other DOACs - andexanet alfa where available, otherwise PCC.
- Report suspected adverse drug reactions to the MHRA Yellow Card scheme, especially for black-triangle medicines.
Worked example
A 78-year-old on ramipril and furosemide is started on ibuprofen for knee pain and returns two weeks later with vomiting and a creatinine of 240 micromol/L (baseline 95). The NSAID is the culprit: stop it, temporarily hold the ACE inhibitor and diuretic, rehydrate, check potassium and review analgesia.
Traps
Prescribing trimethoprim with methotrexate; giving a tetracycline to a child under 12; accepting a vague 'penicillin allergy' without clarifying it; tenfold decimal errors in paediatric syrups.