PLAB 1 Pharmacology and Therapeutics — Questions and Answers
Question 1: A patient is started on warfarin for atrial fibrillation. According to NICE guidelines, what is the target INR range for non-valvular AF?
- 1.0-1.5
- 2.0-3.0 (Correct answer)
- 3.0-4.0
- 4.0-5.0
Correct answer: 2.0-3.0
The target INR for warfarin in non-valvular atrial fibrillation is 2.0-3.0. A higher range (2.5-3.5) is used for mechanical heart valves. DOACs (e.g., apixaban, rivarelbaan) are now recommended first-line for non-valvular AF by NICE, as they do not require INR monitoring.
Question 2: A 55-year-old man presents with an acute ST-elevation myocardial infarction (STEMI). According to NICE and UK guidelines, which combination of antiplatelet drugs should be given immediately?
- Aspirin alone
- Aspirin 300 mg plus a P2Y12 inhibitor (e.g., ticagrelor or clopidogrel) (Correct answer)
- Clopidogrel alone
- Warfarin and aspirin
Correct answer: Aspirin 300 mg plus a P2Y12 inhibitor (e.g., ticagrelor or clopidogrel)
UK guidelines for STEMI recommend dual antiplatelet therapy (DAPT): aspirin 300 mg loading dose plus a P2Y12 inhibitor. Ticagrelor is preferred over clopidogrel for STEMI patients undergoing primary PCI. DAPT is continued for 12 months post-MI.
Question 3: A patient on metformin 1g BD develops an eGFR of 28 mL/min. According to BNF guidelines, what should be done with the metformin?
- Continue at the same dose — renal function does not affect metformin dosing
- Stop metformin — it is contraindicated when eGFR falls below 30 mL/min due to the risk of lactic acidosis (Correct answer)
- Double the dose to compensate for reduced efficacy
- Switch to insulin only if HbA1c rises above 80 mmol/mol
Correct answer: Stop metformin — it is contraindicated when eGFR falls below 30 mL/min due to the risk of lactic acidosis
Metformin should be stopped when eGFR falls below 30 mL/min/1.73m2 due to the risk of lactic acidosis from impaired renal clearance. The dose should be reviewed when eGFR falls below 45, and reduced when below 30. An alternative glucose-lowering agent should be substituted.
Question 4: A GP is prescribing ramipril for a patient with newly diagnosed hypertension. What monitoring is required after starting an ACE inhibitor?
- No monitoring is required
- Renal function and electrolytes should be checked before starting and 1-2 weeks after initiation or dose change (Correct answer)
- Only blood pressure monitoring is needed
- Liver function tests should be checked monthly
Correct answer: Renal function and electrolytes should be checked before starting and 1-2 weeks after initiation or dose change
ACE inhibitors can cause hyperkalaemia and deterioration of renal function, particularly in patients with renovascular disease. BNF and NICE recommend checking U&Es and eGFR before starting, 1-2 weeks after starting or dose increase, and periodically thereafter. A rise in creatinine >30% or fall in eGFR >25% requires specialist review.
Question 5: A patient with epilepsy controlled on sodium valproate discovers she is pregnant. What is the most important concern regarding sodium valproate in pregnancy?
- Sodium valproate has no effect on pregnancy outcomes
- Sodium valproate is a known teratogen with a 10% risk of major congenital malformations and up to 40% risk of neurodevelopmental disorders — the Pregnancy Prevention Programme must be followed (Correct answer)
- Sodium valproate only causes minor cosmetic abnormalities
- Sodium valproate is safe in the first trimester but should be stopped in the third
Correct answer: Sodium valproate is a known teratogen with a 10% risk of major congenital malformations and up to 40% risk of neurodevelopmental disorders — the Pregnancy Prevention Programme must be followed
Sodium valproate is a major teratogen associated with neural tube defects, congenital malformations (10%), and neurodevelopmental disorders including autism and reduced IQ (up to 40%). The MHRA Pregnancy Prevention Programme requires two forms of contraception and annual risk acknowledgement forms for all women of childbearing potential.
Question 6: A patient on simvastatin 40 mg reports new-onset muscle pain and weakness. Blood tests show a creatine kinase (CK) level 10 times the upper limit of normal. What is the most appropriate action?
- Continue simvastatin and reassure the patient
- Stop simvastatin immediately — the elevated CK indicates rhabdomyolysis/myopathy, a serious adverse effect of statins (Correct answer)
- Increase the dose of simvastatin
- Add a fibrate to the simvastatin
Correct answer: Stop simvastatin immediately — the elevated CK indicates rhabdomyolysis/myopathy, a serious adverse effect of statins
Statin-induced myopathy with CK >10x ULN is a serious adverse effect that can progress to rhabdomyolysis and acute kidney injury. The statin must be stopped immediately. After CK normalises, a different statin at a low dose (e.g., pravastatin) may be tried cautiously, or an alternative lipid-lowering agent used.
PLAB 1 Pharmacology and Therapeutics
A patient is started on warfarin for atrial fibrillation.
According to NICE guidelines, what is the target INR range for non-valvular AF?