Increased risk of digoxin-induced cardiotoxic effects. Increased risk of hypomagnesaemia w/ diuretics. May increase INR and prothrombin time w/ warfarin. May increase serum concentration of tacrolimus, saquinavir, methotrexate. May interfere the elimination of drugs metabolised by CYP2C19 (e.g. diazepam). May decrease the bioavailability of ketoconazole, erlotinib and Fe salts. Potentially Fatal: May decrease serum concentration and pharmacological effects of rilpivirine, atazanavir and nelfinavir. May decrease the antiplatelet effects of clopidogrel.