Other adrenoceptor stimulants: Concurrent use of ephedrine with theophylline may result in increased nausea, nervousness, and insomnia.
Anaesthetics: There may be an increased risk of arrhythmias when used with volatile liquid anaesthetics.
Antidepressants: Ephedrine should not be given to patients who are being treated with monoamine oxidase inhibitors as they may cause hypertensive crisis with marked headache, severe hypertension and subarachnoid haemorrhage. Noradrenaline is displaced by ephedrine with the release of large amounts of catecholamine. The interaction may occur up to two weeks after stopping MAOI therapy. There may be an increased risk of arrhythmias when ephedrine is used with tricyclic antidepressants.
Antihypertensives: Loss of blood pressure control has been detected in hypertensive patients undergoing concurrent therapy with ephedrine and adrenergic neurone blocking drugs and may also occur with other antihypertensives.
Antimigraine drugs: Enhanced vasoconstriction and pressor effects with ergotamine or methysergide; concurrent use of ergotamine not recommended (risk of gangrene).
Cardiac glycosides: Increased risk of arrhythmias in patients receiving ephedrine and cardiac glycosides.
Corticosteroids: Ephedrine has been shown to increase the clearance and prolong the half-life of dexamethasone in asthmatic patients.
Oxytocin: Increased risk of vasoconstrictor or pressor effects in patients receiving oxytocin and ephedrine.
Urinary acidifiers/alkalinisers: Effects of ephedrine may be reduced by acidification and increased by alkalinization of the urine.