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Efavirenz is a prescription medication approved by the U.S. Food and Drug Administration (FDA) to treat human immunodeficiency virus type 1 (HIV-1) infection in adults and in children who are at least 3 months old and weigh at least 3.5 kilograms.
Efavirenz is a type of HIV medicine called a non-nucleoside reverse transcriptase inhibitor (NNRTI). It mainly works by blocking reverse transcriptase, an enzyme HIV-1 needs to make more copies of itself.
Doctors prescribe efavirenz when treating HIV-1 in adults and in children who are at least 3 months old and weigh at least 3.5 kilograms. Efavirenz must be used with other antiretroviral medicines to treat HIV-1.
When used as part of combination treatment, efavirenz may lower the amount of HIV-1 in the blood, called the viral load. It may also increase CD4+ T cells, which help the body fight infections. Efavirenz does not cure HIV-1 infection or AIDS.
HIV-1 is the virus that causes acquired immune deficiency syndrome (AIDS).
Take efavirenz on an empty stomach, preferably at bedtime. Taking efavirenz with food can increase the amount of medicine in the body and may increase side effects. Taking it at bedtime may make some nervous system side effects easier to tolerate.
Swallow efavirenz capsules whole with liquid when possible.
If an adult or child cannot swallow capsules, the contents may be mixed with 1 to 2 teaspoons of soft food, such as applesauce, grape jelly, or yogurt. Take the mixture within 30 minutes. Then use a small amount of food to collect and take any medicine left in the container.
Do not eat additional food for two hours afterward.
For young infants who cannot eat solid food, the capsule contents may be mixed with 2 teaspoons of room-temperature prepared infant formula and given with a 10-milliliter oral syringe. Give the mixture within 30 minutes.
Swallow efavirenz tablets whole with liquid. Do not break or crush them.
The usual adult dose of efavirenz is 600 milligrams by mouth once daily with other antiretroviral medicines.
For children taking efavirenz capsules, the dose is based on body weight:
For children taking the tablet formulation, the labeled dose is 600 milligrams once daily for children who weigh at least 40 kilograms. This is given as one 600-milligram tablet.
This information is based on prescribing information, but your healthcare provider may tailor your treatment plan. Always follow their guidance.
Common side effects include:
Efavirenz can cause serious side effects that may require immediate medical attention. These include:
Get medical help right away if you think you are having a serious reaction.
If you or someone you know needs help, you can contact the 988 Suicide & Crisis Lifeline by calling or texting 988 or by using the online chat.
Before starting efavirenz, your doctor will check your liver function.
Before taking efavirenz, tell your doctor if you:
Tell your doctor about all medicines you take, including prescription drugs, over-the-counter medicines, vitamins, and herbal supplements.
Do not take efavirenz if you:
Do not take efavirenz/emtricitabine/tenofovir disoproxil fumarate (Atripla) with efavirenz unless your doctor tells you to.
Do not miss doses or let your supply of efavirenz run out. The amount of virus in your blood may increase, and the virus may become harder to treat.
A pregnancy exposure registry monitors pregnancy outcomes in people exposed to efavirenz. Healthcare providers can help with registration through the Antiretroviral Pregnancy Registry or by calling 800-258-4263.
Efavirenz may harm a fetus and should not be used during the first trimester of pregnancy. If you can become pregnant, you should have a pregnancy test before starting treatment.
Use effective birth control during treatment and for 12 weeks after stopping efavirenz. A barrier method, such as a condom, contraceptive sponge, diaphragm with spermicide, or cervical cap, should always be used with another form of birth control. Hormonal birth control, such as pills, injections, vaginal rings, or implants, may not work as well while taking efavirenz.
Do not breastfeed while taking efavirenz. People with HIV should not breastfeed because HIV can pass to a baby through breast milk.
These answers are fact-checked by our editorial staff.
How effective is efavirenz for HIV?
In one adult study, 69 percent of people taking efavirenz with zidovudine and lamivudine had HIV-1 levels below 400 copies per milliliter at week 48. This was compared with 50 percent of people taking indinavir with zidovudine and lamivudine. At week 168, response rates were 48 percent for efavirenz with zidovudine and lamivudine, 40 percent for efavirenz with indinavir, and 29 percent for indinavir with zidovudine and lamivudine.
In another 48-week study, 63 percent of people taking efavirenz with nucleoside reverse transcriptase inhibitors (NRTIs) had HIV-1 levels below 500 copies per milliliter. The rate was 71 percent for people taking efavirenz with nelfinavir and NRTIs.
How long does efavirenz take to work for HIV?
The studies report HIV treatment results at week 48 and, in one study, through week 168. Efavirenz reaches steady blood levels in about six to 10 days, but the prescribing information does not say exactly how soon HIV levels will drop for each person or when someone will notice improvement.
Can efavirenz interact with other medicines?
Yes. Efavirenz can affect how other medicines work, and other medicines can affect efavirenz. Some combinations may change drug levels, increase side effects, or make treatment less effective.
Tell your doctor about all prescription medicines, over-the-counter medicines, vitamins, and herbal supplements you take. Some medicines should not be taken with efavirenz, while others may need a dose change or closer monitoring. Do not take efavirenz with elbasvir and grazoprevir.
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