With the joint application of St. John's wort with cyclosporine, warfarin, digoxin, steroid preparations, antiviral agents - HIV protease inhibitors (amprenavir, indinavir, nelfinavir, ritonavir, saquinavir) may reduce their activity. The drug is able to enhance the photosensitizing effect of other drugs, including. tetracyclines, sulfonamides, thiazide diuretics, quinolones, piroxicam.