EM · Applied pharmacology for EM

Applied pharmacology for the emergency department

Also known as Resuscitation pharmacology · Emergency department drugs · Antidotes and reversal agents · Drug interactions in the ED · Cytochrome P450 interactions · Pharmacokinetics in special populations · High-alert medications · Look-alike sound-alike drugs · Renal and hepatic dose adjustment · Safe prescribing in the ED

Applied pharmacology for the emergency department — the drug knowledge a consultant exercises under pressure: the resuscitation drugs given from memory (adrenaline, noradrenaline, amiodarone, lignocaine, atropine, calcium, sodium bicarbonate, naloxone, flumazenil, NAC, tranexamic acid) each with dose, route, indication, mechanism, onset and duration; the pharmacokinetic framework of onset, duration, half-life and clearance that decides route and interval; the high-yield drug–drug interactions and the unifying cytochrome-P450 mechanism (warfarin plus macrolides, SSRI plus tramadol, statin plus macrolides); the dose modification in renal, hepatic, paediatric, elderly and pregnant patients; and the differential of the correct versus the incorrect …

medium25 referencesUpdated 2 Sept 202623 min readSource-verified · Sept 2026

Checked against its sources on 2 Sept 2026

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Practise this topic8 MCQs with explanations

Target exams

ACEMFRCEMABEMFRCPCCCFPEMEBEEM

Red flags

Adrenaline 1:1000 (1 mg/mL, intramuscular for anaphylaxis) versus 1:10 000 (0.1 mg/mL, intravenous for arrest) — confusing the concentration and giving the concentrated form intravenously causes cardiac ischaemia and death
Naloxone half-life 60 to 120 minutes (Saari) — shorter than many opioids; titrate 0.4–2 mg to respiration not consciousness; the patient who wakes may re-sedate
Flumazenil in the chronic benzodiazepine user or the mixed overdose precipitates seizures — it is not the universal antidote and has a far narrower role than naloxone
Clarithromycin and erythromycin inhibit CYP3A4 — the same course of clarithromycin raises the warfarin INR to bleeding and the simvastatin level to rhabdomyolysis; azithromycin is the macrolide that does neither
Calcium is not a routine adult OHCA drug — Vallentin 5 mmol CaCl vs saline ROSC 19% vs 27%, stopped early for harm; Korean ALS discourages calcium and buffers in arrest
The 10-fold decimal error in insulin, heparin and opioid — the single most lethal prescribing pattern in the emergency department

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Meet the patient

A 72-year-old care-home resident arrives delirious, bradycardic at 42, BP 96/58, with a nosebleed she cannot stop. Her list reads warfarin, simvastatin, sertraline, ramipril, frusemide, oxybutynin and digoxin. Four days ago her GP started clarithromycin for a cough. The INR is 8.4, the digoxin level is 3.1, the creatinine has doubled, and the CK is 4200.^[7]

This is the polypharmacy patient in whom a single prescription — clarithromycin — has caused warfarin bleeding and statin rhabdomyolysis by CYP3A4 inhibition, and digoxin accumulation by P-glycoprotein inhibition. The candidate who can name both mechanisms explains the whole case from principle; the one who memorises only the warfarin interaction misses the rest.^[7]^[10]^[25]

References25Show

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[2]WOMAN Trial Collaborators. Effect of early tranexamic acid administration on mortality, hysterectomy, and other morbidities in women with post-partum haemorrhage (WOMAN): an international, randomised, double-blind, placebo-controlled trial Lancet, 2017.PMID 28456509
[3]Prescott LF, Illingworth RN, Critchley JA, Stewart MJ, Adam RD, Proudfoot AT. Intravenous N-acetylcystine: the treatment of choice for paracetamol poisoning Br Med J, 1979.PMID 519312
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[7]Hougaard Christensen MM, Bruun Haastrup M, Øhlenschlaeger T, et al. Interaction potential between clarithromycin and individual statins-A systematic review Basic Clin Pharmacol Toxicol, 2020.PMID 31628882
[8]Boyer EW, Shannon M. The serotonin syndrome N Engl J Med, 2005.PMID 15784664
[9]Dunkley EJ, Isbister GK, Sibbritt D, Dawson AH, Whyte IM. The Hunter Serotonin Toxicity Criteria: simple and accurate diagnostic decision rules for serotonin toxicity QJM, 2003.PMID 12925718
[10]Recker MW, Kier KL. Potential interaction between clarithromycin and warfarin Ann Pharmacother, 1997.PMID 9296238
[11]Saari TI, Strang J, Dale O Clinical Pharmacokinetics and Pharmacodynamics of Naloxone Clin Pharmacokinet, 2024.PMID 38485851
[12]Baldo BA. Toxicities of opioid analgesics: respiratory depression, histamine release, hemodynamic changes, hypersensitivity, serotonin toxicity Arch Toxicol, 2021.PMID 33974096
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[14]Leong TD, Mpofu R, Dadan S, et al. A systematic review and meta-analysis of noradrenaline compared to adrenaline in the management of septic shock Afr J Emerg Med, 2025.PMID 40677279
[15]Penninga EI, Graudal N, Ladekarl MB, et al. Adverse events associated with flumazenil treatment for the management of suspected benzodiazepine intoxication: a systematic review with meta-analyses of randomised trials Basic Clin Pharmacol Toxicol, 2016.PMID 26096314
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[17]Vallentin MF, Granfeldt A, Meilandt C, et al. Effect of intravenous or intraosseous calcium vs saline on return of spontaneous circulation in adults with out-of-hospital cardiac arrest: a randomized clinical trial JAMA, 2021.PMID 34847226
[18]Bright MR, Mudannayake R, Fanning J, et al. Intravenous adrenaline (epinephrine): its use in the critical care setting Postgrad Med J, 2026.PMID 41511186
[19]Perkins GD, Couper K. Improving vasopressor use in cardiac arrest Crit Care, 2023.PMID 36864469
[20]Beecham GB, Patel P. Lidocaine StatPearls, 2026.PMID 30969703
[21]Evans L, Rhodes A, Alhazzani W, et al. Surviving sepsis campaign: international guidelines for management of sepsis and septic shock 2021 Intensive Care Med, 2021.PMID 34599691
[22]Kim TY, Ahn GJ, Cha KC, et al. 2025 Korean guidelines for cardiopulmonary resuscitation: part 4. Adult advanced life support Clin Exp Emerg Med, 2026.PMID 42297407
[23]Sprung CL, Annane D, Keh D, et al. Hydrocortisone therapy for patients with septic shock N Engl J Med, 2008.PMID 18184957
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[25]Rengelshausen J, Göggelmann C, Burhenne J, et al. Contribution of increased oral bioavailability and reduced nonglomerular renal clearance of digoxin to the digoxin-clarithromycin interaction Br J Clin Pharmacol, 2003.PMID 12848773