The metabolism of budesonide is primarily mediated by CYP3A4, one of the cytochrome P450 enzymes. Inhibitors of this enzyme, e.g. ketoconazole and itraconazole, can therefore increase the risk of systemic side effects (see Precautions and Side Effects). Other potent inhibitors of CYP3A4 are also likely to markedly increase plasma concentrations levels of budesonide. Therefore, the combination of Talgan with potent CYP3A inhibitors should be avoided and if it is not possible, the period between treatments should be as long as possible. A reduction of the budesonide dose could be considered.
Raised plasma concentrations of and enhanced effects of corticosteroids have been observed in women also treated with oestrogens and contraceptive steroids, but no effect has been observed with budesonide and concomitant intake of low dose combination oral contraceptives.
The suppressive effect on adrenal function is additive if used concomitantly with systemic or intranasal steroids. Because adrenal function may be suppressed, an ACTH stimulation test for diagnosing pituitary insufficiency might show false results (low values).