Orange juice moderately interferes with the gastrointestinal absorption of atenolol. This food-drug interaction can be of clinical significance.

Even a low dose of ciprofloxacin can moderately increase serum concentrations of clozapine and N-desmethylclozapine. A probable mechanism of interaction is an inhibition of CYP1A2 enzyme by ciprofloxacin. The possibility of clinically significant interaction should be considered, especially when higher doses of ciprofloxacin are used concomitantly with clozapine.

Itraconazole markedly increased systemic exposure to inhaled budesonide, probably by inhibiting the cytochrome P4503A4-mediated metabolism of budesonide during both the first-pass and the elimination phases. This interaction resulted in enhanced systemic effects of budesonide, as shown by suppression of cortisol production. Long-term coadministration of budesonide and a potent CYP3A4 inhibitor may be associated with an increased risk of adverse effects of budesonide.