MSRA MSRA Pharmacology and Prescribing 1 — Questions and Answers
Question 1: A patient on warfarin is started on amoxicillin for a chest infection. What is the most likely effect on their INR?
- Decrease in INR
- Increase in INR (Correct answer)
- No change in INR
- Variable effect depending on dose
Correct answer: Increase in INR
Antibiotics reduce gut flora that produce Vitamin K, decreasing its availability and potentiating warfarin's anticoagulant effect, thereby raising the INR.
Question 2: Which of the following is a contraindication to metformin use?
- Type 2 diabetes with HbA1c > 7%
- eGFR < 30 mL/min/1.73m² (Correct answer)
- BMI > 35 kg/m²
- Age > 70 years
Correct answer: eGFR < 30 mL/min/1.73m²
Metformin is contraindicated in severe renal impairment (eGFR < 30) because impaired excretion leads to accumulation and risk of potentially fatal lactic acidosis.
Question 3: A patient presents with an acute gout attack. Which intervention should be avoided during the acute phase?
- Colchicine
- Naproxen
- Initiating allopurinol (Correct answer)
- Prednisolone
Correct answer: Initiating allopurinol
Starting allopurinol during an acute gout attack can mobilise urate crystals and prolong or worsen the attack; it should be initiated 2–4 weeks after resolution.
Question 4: A patient taking an ACE inhibitor develops a persistent dry cough. What is the most appropriate management?
- Add an antihistamine
- Reduce the ACE inhibitor dose
- Switch to an angiotensin receptor blocker (ARB) (Correct answer)
- Add a short-acting beta-agonist inhaler
Correct answer: Switch to an angiotensin receptor blocker (ARB)
ACE inhibitor cough is caused by bradykinin accumulation; switching to an ARB avoids this mechanism while maintaining renin-angiotensin system blockade.
Question 5: A patient on lithium develops coarse tremor, ataxia, and confusion. What is the most likely diagnosis?
- Lithium withdrawal syndrome
- Lithium toxicity (Correct answer)
- Neuroleptic malignant syndrome
- Serotonin syndrome
Correct answer: Lithium toxicity
Lithium toxicity classically presents with coarse tremor (distinct from the fine tremor at therapeutic levels), ataxia, and confusion, progressing to seizures and coma in severe cases.
Question 6: Which best describes the mechanism of action of furosemide?
- Inhibits Na-K-2Cl cotransporter in the loop of Henle (Correct answer)
- Blocks Na-Cl cotransporter in the distal convoluted tubule
- Inhibits carbonic anhydrase in the proximal tubule
- Antagonises aldosterone receptors in the collecting duct
Correct answer: Inhibits Na-K-2Cl cotransporter in the loop of Henle
Furosemide inhibits the NKCC2 (Na-K-2Cl) cotransporter in the thick ascending limb of the loop of Henle, producing powerful diuresis.
Question 7: According to NICE guidelines, which antihypertensive is recommended as first-line for a patient aged 55 or older with uncomplicated hypertension?
- ACE inhibitor
- Beta-blocker
- Calcium channel blocker (Correct answer)
- Thiazide-like diuretic
Correct answer: Calcium channel blocker
NICE recommends a calcium channel blocker as Step 1 treatment for patients aged 55 or over, as renin-angiotensin system blockers are less effective in this age group due to lower plasma renin activity.
MSRA MSRA Pharmacology and Prescribing 1
A patient on warfarin is started on amoxicillin for a chest infection.
What is the most likely effect on their INR?