Approved for medical use in 2006, Efavirenz/emtricitabine/tenofovir is a fixed-dose combination, and is used to treat HIV/AIDS. Basically, all three medicines in this combination interfere with an enzyme called reverse transcriptase, which is used by HIV-infected cells to make more HIV. Since Efavirenz/emtricitabine/tenofovir inhibits, or reduces, the activity of this enzyme, this drug causes HIV-infected cells to slow down or stop producing new viruses. Bear in mind that this medication can cause headache, trouble sleeping, sleepiness, and unsteadiness. As for its serious side effects, they may include high blood lactate levels, psychiatric symptoms, and enlargement of the liver. Efavirenz/emtricitabine/tenofovir should be kept away from children and also from pregnant women as it can harm the baby during the first trimester of pregnancy. Besides, you need to remember that this medication may be taken with or without food, although taking it on an empty stomach is recommended to lower the chance of sleep- related side effects. And if you prefer to take it with food, make sure you choose low-fat foods. In fact, taking Efavirenz/emtricitabine/tenofovir at bedtime may reduce daytime side effects.