Budesonide × Fluvoxamine

Budesonide is broken down mainly by the CYP3A4 enzyme. Fluvoxamine moderately inhibits this enzyme (fluvoxamine SmPC), so budesonide levels may rise, and with them the risk of systemic corticosteroid effects. These effects are less likely with inhaled than with oral budesonide (inhaled budesonide SmPC), but they are possible: with high-dose inhaled budesonide, itraconazole raised its plasma levels about fourfold on average (inhaled budesonide SmPC).

On long-term therapy: moon face, weight gain with fat redistribution, skin thinning, acne, muscle weakness, mood disturbance, hyperglycaemia.

The fluvoxamine SmPC requires drugs metabolised by the CYP3A4 enzyme to be started or adjusted to the low end of their dose range when given with fluvoxamine, with monitoring of their effects and side effects and dose reduction if needed (fluvoxamine SmPC). Oral budesonide should not be combined with CYP3A4 inhibitors unless the benefit outweighs the higher risk of systemic corticosteroid effects; if the combination is used, monitor the patient for these effects (oral budesonide SmPC). The inhaled budesonide SmPC says to avoid strong CYP3A inhibitors and gives itraconazole, ketoconazole, human immunodeficiency virus (HIV) protease inhibitors and cobicistat-containing products as examples. With a 1–2 week course the interaction with inhaled budesonide is of limited relevance; in long-term treatment take it into account, watch for systemic effects and keep the inhaled corticosteroid at the lowest dose that controls asthma (inhaled budesonide SmPC).