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 …

medium24 referencesUpdated 2 Sept 202621 min readVerification in progress

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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 deathNaloxone 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-sedateFlumazenil in the chronic benzodiazepine user or the mixed overdose precipitates seizures — it is not the universal antidote and has a far narrower role than naloxoneClarithromycin 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 neitherCalcium 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 arrestThe 10-fold decimal error in insulin, heparin and opioid — the single most lethal prescribing pattern in the emergency department

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Practise this topic

8 MCQs with explanations

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ACEMFRCEMABEMFRCPCCCFPEMEBEEM

Red flags

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, a CYP3A4 inhibitor — has, by one mechanism, caused warfarin bleeding, statin rhabdomyolysis, and digoxin accumulation. The candidate who can name the unifying enzyme explains the whole case from principle; the one who memorises only the warfarin interaction misses the rest.[7][10]

Emergency Medicine Pro

You have read the opening of this topic. The complete unit — every section and its primary-source references — is part of the Emergency Medicine fellowship atlas.

References24Show ledger

[1]Shakur H, Roberts I, Bautista R, et al. Effects of tranexamic acid on death, vascular occlusive events, and blood transfusion in trauma patients with significant haemorrhage (CRASH-2): a randomised, placebo-controlled trial Lancet, 2010.PMID 20554319
[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
[4]Hoffman JR, Votey SR. Effect of hypertonic sodium bicarbonate in the treatment of moderate-to-severe cyclic antidepressant overdose Am J Emerg Med, 1993.PMID 8216512
[5]Kudenchuk PJ, Cobb LA, Copass MK, et al. Amiodarone for resuscitation after out-of-hospital cardiac arrest due to ventricular fibrillation N Engl J Med, 1999.PMID 10486418
[6]Kudenchuk PJ, Brown SP, Daya M, et al. Amiodarone, Lidocaine, or Placebo in Out-of-Hospital Cardiac Arrest N Engl J Med, 2016.PMID 27043165
[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
[13]Cardona V, Ansotegui IJ, Ebisawa M, et al. World allergy organization anaphylaxis guidance 2020 World Allergy Organ J, 2020.PMID 33204386
[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
[16]Sepulveda EA, Pak A. Lipid emulsion therapy StatPearls, 2026.PMID 31751087
[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
[24]Annane D, Sébille V, Charpentier C, et al. Effect of treatment with low doses of hydrocortisone and fludrocortisone on mortality in patients with septic shock JAMA, 2002.PMID 12186604

Applied pharmacology for the emergency department

medium24 referencesUpdated 2 Sept 202621 min readVerification in progress

Practise this topic

8 MCQs

Meet the patient

Emergency Medicine Pro

You have read the opening of this topic. The complete unit — every section and its primary-source references — is part of the Emergency Medicine fellowship atlas.

References24Show ledger

[1]Shakur H, Roberts I, Bautista R, et al. Effects of tranexamic acid on death, vascular occlusive events, and blood transfusion in trauma patients with significant haemorrhage (CRASH-2): a randomised, placebo-controlled trial Lancet, 2010.PMID 20554319
[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
[4]Hoffman JR, Votey SR. Effect of hypertonic sodium bicarbonate in the treatment of moderate-to-severe cyclic antidepressant overdose Am J Emerg Med, 1993.PMID 8216512
[5]Kudenchuk PJ, Cobb LA, Copass MK, et al. Amiodarone for resuscitation after out-of-hospital cardiac arrest due to ventricular fibrillation N Engl J Med, 1999.PMID 10486418
[6]Kudenchuk PJ, Brown SP, Daya M, et al. Amiodarone, Lidocaine, or Placebo in Out-of-Hospital Cardiac Arrest N Engl J Med, 2016.PMID 27043165
[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
[13]Cardona V, Ansotegui IJ, Ebisawa M, et al. World allergy organization anaphylaxis guidance 2020 World Allergy Organ J, 2020.PMID 33204386
[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
[16]Sepulveda EA, Pak A. Lipid emulsion therapy StatPearls, 2026.PMID 31751087
[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
[24]Annane D, Sébille V, Charpentier C, et al. Effect of treatment with low doses of hydrocortisone and fludrocortisone on mortality in patients with septic shock JAMA, 2002.PMID 12186604