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. Built on the amphetamine cross-reactivity study (Sainz-Pastor 2026), the acute right-ventricular failure vasopressor case report (Mohammed 2026), the cost and environmental comparison of emergency vasopressors (Parkinson 2026), the vasopressor choice and postoperative delirium study in older adults (Dong 2026), the maternal-BMI and metaraminol dosing study (Gao 2026).