Master Clinical Pharmacology & Therapeutics
for MRCP Part 1

What the MRCP Part 1 Tests in Clinical Pharmacology & Therapeutics

MRCP Part 1 Clinical Pharmacology & Therapeutics tests your ability to select the safest and most effective drug for a given clinical scenario, recognise adverse effects and interactions, and apply prescribing guidelines. You must know first-line treatments for common conditions (e.g., hypertension, asthma, diabetes), key contraindications (e.g., NSAIDs in renal impairment), and dose adjustments (e.g., renally excreted drugs). Questions often present a patient with comorbidities, requiring you to choose the drug with the least harm. You must also interpret therapeutic drug monitoring (e.g., lithium, digoxin, warfarin) and recall major drug interactions (e.g., statins with clarithromycin). Emphasis is on clinical decision-making, not pure pharmacology.

High-Yield Concepts

• Anticoagulation Choices: For atrial fibrillation with CHA2DS2-VASc ≥2 in men or ≥3 in women, first-line is a DOAC (apixaban 5 mg BD, rivaroxaban 20 mg OD, or edoxaban 60 mg OD) unless mechanical valve or moderate-severe mitral stenosis. Warfarin remains first-line for mechanical valves (target INR 2.5-3.5 for aortic, 3.0-4.0 for mitral). Remember DOACs are contraindicated in antiphospholipid syndrome with triple positivity.
• Antihypertensive Therapy: NICE guidelines: first-line for age <55 is ACE inhibitor (e.g., ramipril 2.5 mg OD) or ARB if intolerant; for age ≥55 or black African/Caribbean, first-line is CCB (e.g., amlodipine 5 mg OD). Add thiazide-like diuretic (indapamide 2.5 mg OD) as second step. Target clinic BP <140/90 (<130/80 if CKD, diabetes, or CVD).
• Diabetes Pharmacotherapy: Metformin (500 mg BD, max 2 g/day) is first-line for type 2 diabetes if eGFR >30. If HbA1c >58 mmol/mol on metformin, add SGLT2 inhibitor (e.g., dapagliflozin 10 mg OD) in patients with CKD or heart failure; otherwise add DPP-4 inhibitor (e.g., sitagliptin 100 mg OD) or sulfonylurea (e.g., gliclazide 80 mg BD). Insulin is indicated if HbA1c >75 mmol/mol or symptomatic hyperglycaemia.
• Antimicrobial Stewardship: Empiric antibiotics: for community-acquired pneumonia, use amoxicillin 500 mg TDS (severe: co-amoxiclav 625 mg TDS + clarithromycin 500 mg BD). For urinary tract infection in non-pregnant women, nitrofurantoin 100 mg BD (if eGFR >45) or trimethoprim 200 mg BD. Avoid fluoroquinolones as first-line due to tendonitis risk. Always check local resistance patterns.
• Lithium Monitoring: Therapeutic range for maintenance: 0.4-1.0 mmol/L (sampled 12 hours post-dose). Check renal function (eGFR), TFTs, and calcium every 6 months. Toxicity (level >1.5) causes tremor, ataxia, nephrogenic diabetes insipidus; severe (>2.5) may require haemodialysis. Avoid NSAIDs, ACE inhibitors, and thiazide diuretics which increase lithium levels.
• Opioid Prescribing & Equianalgesia: Conversion: oral morphine 10 mg = oral oxycodone 5 mg = transdermal fentanyl 12 mcg/h (in opioid-naive). For breakthrough pain, prescribe immediate-release morphine at 1/6th of total daily dose. Avoid codeine in children <12 and in breastfeeding due to CYP2D6 variability. Naloxone (0.4-2 mg IV) reverses respiratory depression; duration shorter than opioids, may need infusion.
• Drug Interactions with Statins: Simvastatin 80 mg is contraindicated due to myopathy risk. Atorvastatin and simvastatin are metabolised by CYP3A4; avoid concurrent use with strong inhibitors (clarithromycin, itraconazole, HIV protease inhibitors). Pravastatin and rosuvastatin are less affected. Statin-induced myopathy: check CK if muscle symptoms; if CK >10x ULN, stop statin.
• Heart Failure Pharmacotherapy: First-line: ACE inhibitor (e.g., ramipril 2.5-10 mg OD) + beta-blocker (bisoprolol 1.25-10 mg OD or carvedilol 3.125-25 mg BD). If still symptomatic, add spironolactone 25 mg OD (monitor K+). For HFrEF (LVEF <40%), consider SGLT2 inhibitor (dapagliflozin or empagliflozin 10 mg OD). Avoid NSAIDs, verapamil, and diltiazem.

Common Traps in Clinical Pharmacology & Therapeutics Questions

• Confusing the target INR for mechanical mitral valves (3.0-4.0) with aortic valves (2.5-3.5).
• Using amiodarone as first-line for atrial fibrillation in patients with structural heart disease—it has significant pulmonary and thyroid toxicity.
• Prescribing metformin when eGFR is <30 mL/min—risk of lactic acidosis.
• Assuming all beta-blockers are equally safe in asthma—only cardioselective ones (bisoprolol, metoprolol) are relatively safe, but still use with caution.
• Forgetting that digoxin toxicity is potentiated by hypokalaemia (e.g., from diuretics) and that the therapeutic range is 0.5-2.0 mcg/L (but toxicity can occur at lower levels if hypokalaemic).
• Giving IV potassium chloride undiluted or too rapidly—maximum rate is 10 mmol/hour via peripheral line, and 20 mmol/hour via central line with ECG monitoring.

How to Revise Clinical Pharmacology & Therapeutics for the MRCP Part 1

Focus on NICE and BNF guidelines for common conditions: hypertension, diabetes, heart failure, asthma, and anticoagulation. Questions often present a patient with multiple comorbidities (e.g., CKD + AF + diabetes) and ask which drug is safest. Practise calculating eGFR-based dosing (e.g., for gabapentin, enoxaparin). Memorise key contraindications (e.g., NSAIDs in CKD, ACE inhibitors in pregnancy) and major drug interactions (e.g., warfarin + antibiotics). Review adverse effect profiles of high-yield drugs: methotrexate (pneumonitis, myelosuppression), amiodarone (thyroid, pulmonary fibrosis), and corticosteroids (osteoporosis, hyperglycaemia). Use past MRCP Part 1 questions to identify recurring themes.

Practise it: MedLumen has 50 Clinical Pharmacology & Therapeutics questions for the MRCP Part 1, each with a full explanation and references.