Ephedrine

Even at ordinary doses it can raise blood pressure and heart rate and cause palpitations, anxiety, and insomnia; larger or repeated doses risk arrhythmias, chest pain, and in rare cases stroke, especially in people with heart conditions. Old weight-loss stacks pairing it with caffeine were linked to serious cardiovascular events. It is dangerous with MAOIs and other stimulants, which can cause a sharp blood-pressure spike. Not medical advice.

Ephedrine works largely by releasing stored noradrenaline, and that indirect mechanism is what makes its interactions dangerous.

Monoamine oxidase inhibitors are the worst of them. With MAO blocked, nerve terminals hold enlarged releasable stores, so a routine dose of ephedrine can produce a hypertensive crisis with headache, arrhythmia or stroke. The risk persists for about two weeks after an irreversible MAO inhibitor is stopped. Oxytocin and other oxytocic drugs also augment the pressor response, and serious postpartum hypertension with stroke has been reported with the pair. Clonidine, atropine and propofol likewise amplify the blood pressure rise.

Alpha and beta adrenergic antagonists blunt the pressor effect at the receptor, so ephedrine works poorly against them. Halogenated volatile anesthetics sensitize the myocardium to catecholamines, which raises the chance of ventricular arrhythmia.

Ephedrine is a weak base cleared largely unchanged by the kidney, so urinary alkalinizers such as acetazolamide and sodium bicarbonate slow its elimination and prolong both effect and side effects.

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