USE OF TENOFOVIR DISOPROXIL FUMARATE WITH NEPHROTOXIC DRUGS OR WITH OTHER DRUGS ELIMINATED BY ACTIVE TUBULAR SECRETION IS NOT RECOMMENDED; IF SUCH USE IS UNAVOIDABLE, RENAL FUNCTION SHOULD BE MONITORED WEEKLY. TENOFOVIR INCREASE THE PLASMA CONCENTRATIONS OF DIDANOSINE. ONCE DAILY TRIPLE NUCLEOSIDE REGIMENS OF TENOFOVIR AND LAMIVUDINE WITH EITHER ABACAVIR OR DIDANOSINE ARE ASSOCIATED WITH A HIGH LEVEL OF TREATMENT FAILURE AND OF EMERGENCE OF RESISTANCE, AND SHOULD BE AVOIDED. DECREASED PLASMA CONCENTRATIONS OF ATAZANAVIR ALSO OCCUR WHEN TENOFOVIR IS GIVEN CONCOMITANTLY; THE EFFECT IS SIGNIFICANTLY REDUCED WHEN RITONAVIR IS ADDED AS A BOOSTER. USE OF LOPINAVIR/RITONAVIR WITH TENOFOVIR MODESTLY INCREASES THE PLASMA CONCENTRATIONS OF TENOFOVIR & CHANCES OF ITS SIDE EFFECTS.