Coadministration with emtricitabine has not been studied. Based on metabolism and clearance a clinically significant interaction is unlikely as diclofenac is partly glucuronidated by UGT2B7 and partly oxidized by CYP2C9. However, diclofenac could potentially decrease renal elimination of tenofovir (thereby increasing the risk of nephrotoxicity) as diclofenac is a strong inhibitor of MRP4. A retrospective analysis showed that patients treated with diclofenac together with tenofovir-DF containing regimens were at higher risk of developing an acute kidney injury when compared to patients treated with tenofovir-DF-sparing regimens. Since diclofenac can exacerbate tenofovir-DF nephrotoxicity, diclofenac should be used with caution with emtricitabine/tenofovir-DF and close monitoring of renal function is recommended.