Coadministration has not been studied. Ketoprofen is mainly metabolized by multiple UGTs. Emtricitabine and tenofovir (derived from tenofovir-DF) are eliminated renally. No interaction is expected with emtricitabine but renal elimination of tenofovir-DF could potentially decrease, thereby increasing the risk of nephrotoxicity. Cases of acute renal failure after initiation of high dose or multiple NSAIDs have been reported in patients treated with tenofovir-DF and with risk factors for renal dysfunction. The risk is also increased if an NSAID is used for a long duration, if the patient has a pre-existing renal dysfunction, has a low body weight, or receives other drugs that may increase tenofovir exposure. Alternatives to NSAIDs should be considered in patients at risk for renal dysfunction. If emtricitabine/tenofovir-DF is co-administered with an NSAID, renal function should be monitored adequately.