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Drug of Choice Cheatsheet — ID (MRCP Part 1)

TL;DR

This drug of choice cheatsheet — infectious diseases focus (MRCP Part 1) distils the most testable first-line antimicrobial choices you must recall quickly in the exam. It covers 12 high-yield infections, a short MRCP-style case, and a practical revision checklist. Use it to anchor infectious-disease pharmacology to predictable blueprint patterns. Ideal before mocks or timed blocks.


Why this matters

In MRCP Part 1, antimicrobial therapy questions frequently turn on a single decisive clue: age, exposure, pregnancy, immunosuppression, travel, or recent antibiotic use. You are not asked to prescribe in real-world depth, but you must recognise standard first-line, guideline-consistent agents. This cheatsheet helps you consolidate those defaults without memorising entire guideline PDFs.

For exam structure and blueprint context, see the MRCP Part 1 overview at https://crackmedicine.com/mrcp-part-1/.


High-yield infectious diseases: drug-of-choice list

The following table summarises 12 exam-relevant infections with their standard high-level first-line options. These are aligned with widely used UK clinical references, including NICE (antimicrobial guidance), UKHSA, and exam-style expectations.


Drug of Choice Cheatsheet — Infectious Diseases (MRCP Part 1)

Infection / Scenario

First-line Drug

High-yield Clue

Meningococcal meningitis

IV ceftriaxone

Purpuric rash, rapid onset

Pneumococcal meningitis

IV ceftriaxone ± dexamethasone

Cranial symptoms + lobar consolidation history

Listeria meningitis

IV amoxicillin/ampicillin

Elderly, alcoholism, pregnancy, immunosuppression

Severe community-acquired pneumonia

IV co-amoxiclav + macrolide

CURB-65 ≥3

Atypical pneumonia (Mycoplasma/Chlamydia)

Macrolide (azithromycin/clarithromycin)

Young adult + dry cough + haemolysis

Legionella pneumonia

Macrolide or quinolone

Hyponatraemia + diarrhoea

Clostridioides difficile infection

Oral vancomycin

Recent antibiotics; watery diarrhoea

Gonorrhoea

IM ceftriaxone

Purulent discharge

Chlamydia

Doxycycline

Dysuria post sexual contact

Cellulitis (non-purulent)

Flucloxacillin

Limb erythema + fever

Erysipelas

Penicillin V

Sharp, raised borders

Plasmodium falciparum malaria (uncomplicated)

Artemisinin-based combination therapy (ACT)

Travel to Africa/Asia

Authoritative guidance sources referenced:


Five most tested subtopics in MRCP ID pharmacology

  1. CNS infections

    • Identify Listeria risk groups (elderly, pregnancy, alcoholism, immunosuppressed).

    • Distinguish meningococcal vs pneumococcal clinical clues.

  2. Resistant organisms

    • MRSA → think vancomycin/teicoplanin (high-level exam clue, not deep stewardship).

  3. Sexually transmitted infections

    • Gonorrhoea = ceftriaxone IM (rising resistance makes this a favourite test point).

  4. Pneumonia patterns

    • Atypicals vs Legionella vs classic pneumococcus presentations.

  5. Gastrointestinal infections

    • C. difficile: avoid metronidazole except in limited circumstances; vancomycin is standard.


Practical study tips (exam-directed)

  1. Learn by syndrome, not by organism.

  2. Anchor therapy to patient type (pregnant, elderly, immunosuppressed → red flags).

  3. Link clinical clue → most likely pathogen → first-line agent.

  4. Use spaced repetition: 20–30 ID therapy cards reviewed every 48 hours.

  5. Practise using mocks: attempt a block from your Free MRCP MCQs (https://crackmedicine.com/qbank/) and a timed session via Start a mock test (https://crackmedicine.com/mock-tests/).

  6. Review NICE and UKHSA summaries, not full guidance—focus on common infections.

Flat-lay of medical study notes for MRCP Part 1 infectious diseases drug of choice revision.

Practical example / Mini-case (MRCP style)

A 72-year-old man with alcohol dependence presents with fever, neck stiffness, and reduced GCS. CT head is normal. CSF shows: high protein, low glucose, and lymphocyte predominance.

Most appropriate initial antimicrobial therapy?

Answer: IV ampicillin/amoxicillin (for Listeria risk).

Explanation: Elderly age and alcoholism increase risk of Listeria monocytogenes, which is not reliably covered by third-generation cephalosporins. This is a classic MRCP clue; ceftriaxone alone would be inadequate.


Five common traps candidates fall into

  • Confusing atypical pneumonia regimens: MRCP expects macrolides for Mycoplasma/Chlamydia; fluoroquinolones mainly flagged in Legionella.

  • Overusing metronidazole in C. difficile: Modern UK practice emphasises oral vancomycin first line.

  • Missing pregnancy-related contraindications: Avoid doxycycline and quinolones.

  • Thinking penicillin allergy automatically means “avoid β-lactams entirely”: Cephalosporins are often acceptable unless anaphylaxis.

  • Choosing broad-spectrum therapy unnecessarily: MRCP wants the standard first-line, not escalation.


FAQs

1) How many “drug of choice” items do I need to memorise for MRCP Part 1?

Roughly 20–30 high-frequency infections repeatedly appear across resources. Focus on CNS infections, pneumonia subtypes, STIs, SSTIs, and C. difficile.

2) How accurate must dosing knowledge be?

Doses are not required. MRCP tests recognition of first-line antimicrobial choices, not exact schedules.

3) Are guidelines like NICE essential to memorise?

No. Use NICE for conceptual alignment but revise concise exam-focused tables such as this cheatsheet.

4) How do I practise ID therapy questions effectively?

Use mixed timed blocks (20–50 questions) and review errors immediately. Try the Free MRCP MCQs and mock tests to simulate exam pacing.

5) Should I revise resistant organisms in depth?

Only high-yield patterns: MRSA → glycopeptides; ESBL → carbapenems; atypical coverage → macrolides.


Ready to start?

If this cheatsheet helped consolidate your ID pharmacology, strengthen your preparation with our Free MRCP MCQs, full mock tests, and structured content in the MRCP Part 1 overview. Continue with our sibling article, Study Plan for MRCP Part 1, for a complete 10-week roadmap.


Sources

 
 
 

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