Increased tacrolimus blood levels w/ CYP3A4 inhibitors: antifungal agents eg, ketoconazole, fluconazole, itraconazole, voriconazole; erythromycin; HIV protease inhibitors eg, ritonavir, nelfinavir, saquinavir, HCV protease inhibitors eg, telaprevir, boceprevir; clotrimazole, clarithromycin, josamycin, nifedipine, nicardipine, diltiazem, verapamil, amiodarone, danazol, ethinylestradiol, omeprazole, nefazodone, herbal remedies containing extr of Schisandra sphenanthera; bromocriptine, cortisone, dapsone, ergotamine, gestodene, lidocaine, mephenytoin, miconazole, midazolam, nilvadipine, norethindrone, quinidine, tamoxifen, (triacetyl)oleandromycin; grapefruit juice; lansoprazole, ciclosporin. Increased tacrolimus blood levels w/ other active substances known to have high affinity for plasma proteins (eg, NSAIDs, oral anticoagulants, oral antidiabetics); prokinetic agents (eg, metoclopramide); cimetidine; Mg-Al hydroxide. Decreased tacrolimus blood levels w/ rifampicin, phenytoin, St. John's wort; phenobarb; maintenance doses of corticosteroids; carbamazepine, metamizole, INH. Increased or decreased tacrolimus blood levels w/ high dose prednisolone or methylprednisolone. May affect metabolism of CYP3A4 substrates. Prolonged t½ of ciclosporin. Synergistic/additive nephrotoxic effects w/ ciclosporin. Increased blood levels of phenytoin. Reduced clearance of steroid-based contraceptives. Increased toxic effects w/ medicinal products known to have nephrotoxic or neurotoxic effects (eg, aminoglycosides, gyrase inhibitors, vancomycin, cotrimoxazole, NSAIDs, ganciclovir or acyclovir). Enhanced nephrotoxicity w/ amphotericin B & ibuprofen. Increased risk of hyperkalaemia w/ high K intake or K-sparing diuretics.