Anaes · Anaesthetic adjuncts
Ephedrine
Also known as Mixed-acting sympathomimetic · Natural Ephedra alkaloid · Indirect noradrenaline-releasing vasopressor · Alpha and beta adrenergic agonist
Ephedrine is a NATURAL ALKALOID from Ephedra sinica and a mixed-acting sympathomimetic, distinct from the pure alpha-1 agonists because it raises BOTH blood pressure and heart rate. Its dominant mechanism is INDIRECT — it is taken up into sympathetic nerve terminals and displaces noradrenaline from storage vesicles, on top of WEAK direct alpha-1, beta-1 and beta-2 agonism. The released noradrenaline drives the characteristic rise in heart rate, contractility and cardiac output (beta-1) together with the rise in blood pressure (alpha-1 vasoconstriction plus the cardiac output), which is why ephedrine supports a bradycardic hypotensive patient in a way that phenylephrine cannot. Its exam-defining liability is that it CROSSES THE PLACENTA, where fetal beta-1 stimulation causes tachycardia and a raised metabolic rate that predispose to fetal metabolic acidosis; this is the central reason phenylephrine has displaced ephedrine as the first-line vasopressor for obstetric spinal hypotension. The agent is structurally related to amphetamine and so cross-reacts with amphetamine on urine drug screens (Sainz-Pastor 2026), produces tachyphylaxis as noradrenaline stores are depleted, and has a longer duration of action than phenylephrine at about 60 to 90 minutes after an IV bolus (taught kinetics; no kinetic primary in-file). Built on the amphetamine cross-reactivity study (Sainz-Pastor 2026, immunoassay scope only), the right-ventricular-collapse rescue case report (Mohammed 2026, single-case rescue scope only), the cost and environmental comparison of emergency vasopressors (Parkinson 2026, stewardship scope only), the vasopressor choice and postoperative delirium study in older adults (Dong 2026, delirium-null scope only), and the ephedrine-versus-phenylephrine obstetric systematic review (Lee 2002, 7-RCT scope).
Checked against its sources on 11 Sept 2026
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Red flags
- Ephedrine CROSSES THE PLACENTA and causes fetal beta-1 stimulation — fetal tachycardia and a raised fetal metabolic rate that drive fetal metabolic acidosis. Phenylephrine, which does not cross the placenta to any clinically important extent, is now preferred over ephedrine for obstetric spinal hypotension; this is the single most examined ephedrine fact.
- Ephedrine is structurally related to amphetamine and CROSS-REACTS WITH AMPHETAMINE on urine drug screens. A positive amphetamine screen in a perioperative patient who received ephedrine is a well-recognised false-positive pattern that requires confirmatory testing (Sainz-Pastor 2026).
- TACHYPHYLAXIS occurs with repeated dosing because the indirect mechanism depends on a finite pool of noradrenaline in sympathetic nerve terminals; as those stores are depleted, successive doses produce a diminishing response. Do not expect sustained efficacy from repeated boluses.
- Ephedrine raises heart rate and myocardial oxygen demand and can precipitate tachyarrhythmias and ischaemia in the patient with coronary disease, hypertrophic cardiomyopathy, or a tachycardia-dependent arrhythmia. Avoid it where tachycardia is undesirable and prefer a pure alpha-1 agonist such as phenylephrine.
- Ephedrine crosses the blood-brain barrier and produces CNS stimulation — anxiety, restlessness and insomnia — and can aggravate the patient at risk of postoperative delirium, a relevant consideration in older adults (Dong 2026).
Meet the patient
A 30-year-old, otherwise fit, has just had a spinal for a caesarean section. The blood pressure is falling and the heart rate has drifted down to 48. The registrar reaches for ephedrine — the agent they were taught as first-line for obstetric spinal hypotension. The question that decides the next minute is the single most examined ephedrine fact: should it be ephedrine, or phenylephrine? The systematic-review answer is phenylephrine on fetal acid-base grounds (higher umbilical-artery pH — Lee 2002 [6]).[6]
Hold two properties and the answer is fixed: ephedrine is mixed-acting (indirect plus weak direct), so it raises heart rate and cardiac output alongside blood pressure; and it is lipid-soluble, so it crosses the placenta and the blood-brain barrier (taught pharmacology — the cross-reactivity study [1] owns no barrier claim and the cost comparison [3] owns no kinetic claim). Both properties are what make it useful in one setting (the bradycardic patient) and dangerous in another (the parturient).[1][3]
References5ShowHide
- [1]Sainz-Pastor N, et al. Challenges in the interpretation of amphetamine results: differences of reactivity between immunoassay and immunochromatography Scand J Clin Lab Invest, 2026.PMID 42364133
- [2]Mohammed M, et al. A case report of acute right ventricular failure in a patient undergoing transoesophageal echocardiogram for evaluation of tricuspid regurgitation Eur Heart J Case Rep, 2026.PMID 42339184
- [3]Parkinson EA, et al. The Financial and Environmental Cost of Anaesthetic Emergency Drugs: Comparing Ampoules With Prefilled Syringes. Cureus, 2026.PMID 42005180
- [4]Dong T, et al. Vasopressor Selection and Postoperative Delirium in Older Adults: A Propensity-Matched Database Analysis Semin Cardiothorac Vasc Anesth, 2026.PMID 42359892
- [6]Lee A, et al. A quantitative, systematic review of randomized controlled trials of ephedrine versus phenylephrine for the management of hypotension during spinal anesthesia for cesarean delivery Anesth Analg, 2002.PMID 11916798