Fosrenol may increase gastric pH. Therefore, it is recommended that compounds that are known to interact with antacids should not be taken within 2 hrs of dosing with Fosrenol (eg, chloroquine, hydroxychloroquine and ketoconazole). Interactions with drugs eg, tetracycline, doxycycline and floxacins are theoretically possible. Therefore, it is recommended that they are not taken within 2 hrs of dosing Fosrenol.