You should not take this medication if you are allergic to emtricitabine (Emtriva) or tenofovir (Viread).
Do not take this medication with other medicines that also contain emtricitabine or tenofovir (Atripla, Emtriva, Viread), or lamivudine (Combivir, Epivir, Epzicom, or Trizivir).
Some people have developed a life-threatening condition called lactic acidosis while taking emtricitabine and tenofovir. Early signs of lactic acidosis generally get worse over time and this condition can be fatal. Get emergency medical help if you have even mild symptoms of lactic acidosis, such as: muscle pain or weakness, numb or cold feeling in your arms and legs, trouble breathing, stomach pain, nausea with vomiting, slow or uneven heart rate, dizziness, or feeling very weak or tired.
Emtricitabine and tenofovir can cause severe or fatal liver problems. Call your doctor at once if you have symptoms such as nausea, stomach pain, low fever, loss of appetite, dark urine, clay-colored stools, or jaundice (yellowing of the skin or eyes).