Sympathomimetic agents/Oxytocin:
Adrenaline/epinephrine should not be administered concomitantly with other sympathomimetic agents because of the possibility of additive effects and increased toxicity.
Alpha-adrenergic blocking agents:
Alpha-blockers such as phentolamine antagonise the vasoconstriction and hypertension effects of adrenaline. This effect may be beneficial in adrenaline overdose. (See section 4.9).
Because of their alpha-adrenergic blocking properties, ergot alkaloids can reverse the pressor response to adrenaline.
Beta-adrenergic blocking agents:
Severe hypertension and reflex bradycardia may occur with non-selective beta-blocking drugs such as propranolol, due to alpha-mediated vasoconstriction.
Beta-blockers, especially non-cardioselective agents, also antagonise the cardiac and bronchodilator effects of adrenaline. Patients with severe anaphylaxis who are taking non-cardioselective beta-blockers may not respond to adrenaline treatment.
General anaesthetics
Administration of adrenaline/epinephrine in patients receiving cyclopropane or halogenated hydrocarbon general anaesthetics that increase cardiac irritability and seem to sensitise the myocardium to adrenaline/epinephrine may result in arrhythmias including ventricular premature contractions, tachycardia, or fibrillation (See section 4.4)..
Prophylactic administration of lignocaine or prophylactic administration of propranolol 0.05mg/kg may protect against ventricular irritability if adrenaline/epinephrine is used during anaesthesia with a halogenated hydrocarbon anaesthetic.
Other Drugs:
Adrenaline/epinephrine should not be used in patients receiving high dosage of other drugs (e.g. cardiac glycosides) that can sensitise the heart to arrhythmias. some antihistamines (e.g. diphenhydramine) and thyroid hormones may potentiate the effects of adrenaline/epinephrine, especially on heart rhythm and rate.
Antidepressant agents:
Tricyclic antidepressants such as imipramine, inhibit reuptake of directly acting sympathomimetic agents, and may potentiate the effect of adrenaline, increasing the risk of development of hypertension and cardiac arrhythmias
Although monoamine oxidase (M.A.O.) is one of the enzymes responsible for adrenaline metabolism, M.A.O. inhibitors do not markedly potentiate the effects of adrenaline.
.
Antihypertensive agents:
Adrenaline specifically reverses the antihypertensive effects of adrenergic neurone blockers such as guanethidine, with the risk of severe hypertension. Adrenaline increases blood pressure and may antagonise the effects of antihypertensive drugs.
Phenothiazine:
Phenothiazines block alpha-adrenergic receptors.
Adrenaline/epinephrine should not be used to counteract circulatory collapse or hypotension caused by phenothiazines: a reversal of adrenaline/epinephrine's pressor effects resulting in further lowering of blood pressure may occur.
Hypokalaemia:
The hypokalaemic effect of adrenaline may be potentiated by other drugs that cause potassium loss, including corticosteroids, potassium-depleting diuretics, aminophylline and theophylline.
Hyperglycaemia:
Adrenaline-induced hyperglycaemia may lead to loss of blood-sugar control in diabetic patients treated with insulin or oral hypoglycaemic agents.