Pharmacokinetic interactions: The metabolism of budesonide is primarily mediated by the enzyme CYP3A4. Potent CYP3A4 inhibitors may therefore increase plasma levels of budesonide. This is of limited clinical importance for short-term (1-2 weeks) treatment with potent CYP3A4 inhibitors, but should be taken into consideration during long-term treatment.
If a patient requires, long-term concomitant treatment with Symbicort and a potent CYP3A4 inhibitors, the benefit should be weighed against the increased risk of systemic corticosteroid side effects, patients should be monitored for corticosteroid side effects and/or a reduction of the inhaled corticosteroid dose could be considered.
Pharmacodynamic interactions: Beta-adrenergic blockers can weaken or inhibit the effect of formoterol. Symbicort should therefore not be given together with beta-adrenergic blockers (including eye drops) unless there are compelling reasons.
Concomitant treatment with quinidine, disopyramide, procainamide, phenothiazines, antihistamines (terfenadine) and tricyclic anti-depressants can prolong the QTc-interval and increase the risk of ventricular arrhythmias.
In addition, L-Dopa, L-thyroxine, oxytocin and alcohol can impair cardiac tolerance towards β2 sympathomimetics.
Concomitant treatment with monoamine oxidase inhibitors including agents with similar properties such as furazolidone and procarbazine may precipitate hypertensive reactions.
There is an elevated risk of arrhythmias in patients receiving concomitant anaesthesia with halogenated hydrocarbons.
Concomitant use of other beta-adrenergic drugs can have a potentially additive bronchodilating effect.
Hypokalaemia may increase the disposition towards arrhythmias in patients who are treated with digitalis glycosides.
Hypokalaemia may result from beta2-agonist therapy and may be potentiated by concomitant treatment with xanthine derivatives, corticosteroids and diuretics (see Precautions).
Budesonide and formoterol have not been observed to interact with any other drugs used in the treatment of asthma.
Paediatric population: Interaction studies have only been performed in adults.