May increase plasma conc of drugs eliminated via OCT2 or MATE1 (dofetilide & metformin). Reduced therapeutic effect w/ drugs that induce UGT1A1, UGT1A3, UGT1A9, BCRP & P-gp. Decreased conc w/ etravirine, efavirenz, nevirapine, fosamprenavir/ritonavir, tipranavir/ritonavir, carbamazepine, oxcarbazepine, phenytoin, phenobarb, St. John's wort, drugs containing polyvalent cations (eg, Mg or Al), antacids or laxatives sucralfate, buffered medications, oral Ca or Fe supplements, metformin, rifampicin.