CONCURRENT USE OF ANTICOAGULANTS, COUMARIN OF INDANDIONE DERIVATIVE MAY INCREASE BLEEDING OR PROTHROMBIN TIME. CONCURRENT ADMINISTRATION OF DIGOXIN MAY CAUSE A SLIGHT ELEVATION IN SERUM DIGOXIN CONCENTRATION. CONCURRENT USE OF CHOLESTYRAMINE OR COLESTRIPOL MAY DECREASE THE BIOAVAILABILITY OF SIMVASTATIN. THERE IS INCREASED RISK OF RHABODMYOLYSIS AND ACUTE RENAL FAILURE WITH CONCUREENT USE OF CYCLOSPORINE, ERYTHROMYCIN, GEMFIBROZIL, IMMUNOSUPPRESANTS OR NIACIN.