Enzyme-inducing drugs eg, rifampicin and phenytoin significantly reduce the oral bioavailability of itraconazole. Consequently, monitoring of the Sporal plasma concentrations is advised when enzyme-inducing agents are co-administered.
In vitro studies have shown that there are no interactions on the plasma protein-binding between Sporal and imipramine, propranolol, diazepam, cimetidine, indomethacin, tolbutamide and sulfamethazine.
An interaction with cyclosporin A has been documented. Consequently, the dosage of cyclosporin A, if co-administered with itraconazole, should be reduced if necessary.
An interaction with warfarin and digoxin has been reported. Therefore, the dosage of these drugs, if co-administered with itraconazole, should be reduced if necessary.
An interaction has also been observed with terfenadine and astemizole. Therefore terfenadine and astemizole should not be used by patients treated with Sporal.
No interaction of Sporal with AZT (zidovudine) has been observed.
No inducing effects of Sporal on the metabolism of ethinyloestradiol and norethisterone were observed.