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Generic Name: efavirenz (e FAV ir enz)
Brand Name: Sustiva

Medically reviewed on February 22, 2017

What is efavirenz?

Efavirenz is an antiviral medicine that prevents human immunodeficiency virus (HIV) from multiplying in your body.

Efavirenz is used to treat HIV, the virus that can cause acquired immunodeficiency syndrome (AIDS). Efavirenz is for adults and children who are at least 3 months old and weigh at least 8 pounds. Efavirenz is not a cure for HIV or AIDS.

Efavirenz may also be used for purposes not listed in this medication guide.

Important Information

Do not take efavirenz together with Atripla (combination efavirenz, emtricitabine, and tenofovir), unless your doctor tells you to.

Before taking this medicine

You should not use this medicine if you have ever had a severe allergic reaction to efavirenz. Do not take with Atripla (combination efavirenz, emtricitabine, and tenofovir), unless your doctor tells you to.

To make sure efavirenz is safe for you, tell your doctor if you have:

Do not use efavirenz if you are pregnant. It could harm the unborn baby. Use 2 forms of birth control, including a barrier form (such as a condom or diaphragm with spermicide gel) while you are taking efavirenz, and for at least 12 weeks after your last dose. Tell your doctor if you become pregnant during treatment.

Hormonal contraception (birth control pills, injections, implants, skin patches, and vaginal rings) may not be effective enough to prevent pregnancy while you are taking efavirenz.

HIV can be passed to your baby if you are not properly treated during pregnancy. Take all of your HIV medicines as directed to control your infection.

Women with HIV or AIDS should not breast-feed a baby. Even if your baby is born without HIV, the virus may be passed to the baby in your breast milk.

How should I take efavirenz?

Follow all directions on your prescription label. Do not take this medicine in larger or smaller amounts or for longer than recommended.

Efavirenz must be given in combination with other antiviral medications and it should not be used alone. Your disease may become resistant to efavirenz if you do not take it in combination with other HIV medicines your doctor has prescribed.

Take efavirenz on an empty stomach at bedtime.

To make swallowing easier, you may open an efavirenz capsule and sprinkle the medicine into a spoonful of applesauce, yogurt, or grape jelly. You may also mix the medicine with infant formula if you are giving the medicine to a baby. Swallow the mixture right away. Do not save it for later use.

After taking efavirenz using the sprinkle method, do not eat for the next 2 hours. Efavirenz mixed with infant formula should be given to the baby right away. But do not feed the baby any more formula for at least 2 hours afterward.

Efavirenz comes with instructions for mixing the capsule contents with soft food or infant formula. Follow these directions carefully. Ask your pharmacist if you have any questions.

Do not crush, chew, or break an efavirenz tablet. Swallow it whole with liquid.

While using efavirenz, you may need frequent blood tests.

Efavirenz can cause you to have a false positive drug screening test. If you provide a urine sample for drug screening, tell the laboratory staff that you are taking efavirenz.

If a child is using this medicine, tell your doctor if the child has any changes in weight. Efavirenz doses are based on weight in children, and any changes may affect your child's dose.

Take efavirenz regularly to get the most benefit. Get your prescriptions refilled before you run out of medicine completely. Skipping doses may increase the risk of your virus becoming resistant to antiviral medicine.

Store at room temperature away from moisture and heat.

Read the medication guide provided with all your medications. Do not change your doses or medication schedule without your doctor's advice. Every person with HIV or AIDS should remain under the care of a doctor.

What happens if I miss a dose?

Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while taking efavirenz?

Efavirenz may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert.

Drinking alcohol can increase certain side effects of efavirenz.

Taking this medication will not prevent you from passing HIV to other people. Do not have unprotected sex or share razors or toothbrushes. Talk with your doctor about safe ways to prevent HIV transmission during sex. Sharing drug or medicine needles is never safe, even for a healthy person.

Efavirenz side effects

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have:

  • a seizure (convulsions);

  • liver problems--nausea, upper stomach pain, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes); or

  • severe skin reaction--fever, sore throat, swelling in your face or tongue, redness or burning in your eyes, skin pain, followed by a red or purple skin rash that spreads (especially in the face or upper body) and causes blistering and peeling.

Efavirenz may cause serious psychiatric symptoms including confusion, severe depression (feeling sad or hopeless), suicidal thoughts, anxiety, paranoia, hallucinations, trouble speaking or moving, or unusual behavior. Contact your doctor at once if you have any of these side effects, even if you have had them before.

Efavirenz may increase your risk of certain infections or autoimmune disorders by changing the way your immune system works. Symptoms may occur weeks or months after you start treatment with efavirenz. Tell your doctor if you have:

  • signs of a new infection--fever, night sweats, swollen glands, mouth sores, diarrhea, stomach pain, weight loss;

  • chest pain (especially when you breathe), dry cough, wheezing, feeling short of breath;

  • cold sores, sores on your genital or anal area;

  • rapid heart rate, feeling anxious or irritable, weakness or prickly feeling, problems with balance or eye movement;

  • trouble speaking or swallowing, severe lower back pain, loss of bladder or bowel control; or

  • swelling in your neck or throat (enlarged thyroid), menstrual changes, impotence, loss of interest in sex.

Common side effects may include:

  • nausea, vomiting;

  • dizziness, drowsiness, trouble concentrating;

  • mild skin rash;

  • headache, tired feeling;

  • sleep problems (insomnia), strange dreams; or

  • changes in the shape or location of body fat (especially in your arms, legs, face, neck, breasts, and waist).

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

See also: Side effects (in more detail)

Efavirenz dosing information

Usual Adult Dose for HIV Infection:

600 mg orally once a day

-This drug should be used with a protease inhibitor and/or NRTIs.

Use: In combination with other antiretroviral agents, for the treatment of HIV-1 infection

Usual Adult Dose for Nonoccupational Exposure:

US CDC recommendations: 600 mg orally once a day
Duration of therapy: 28 days

-This drug should be used with (lamivudine or emtricitabine) plus (zidovudine or tenofovir); recommended as the preferred NNRTI-based regimen for nonoccupational postexposure prophylaxis of HIV infection.
-Prophylaxis should be started as soon as possible, within 72 hours of exposure.
-Not approved by US FDA.

Usual Adult Dose for Occupational Exposure:

US Public Health Service working group recommendations: 600 mg orally once a day
Duration of therapy: 28 days, if tolerated

-An alternative antiretroviral agent for use as HIV postexposure prophylaxis only with expert consultation
-Prophylaxis should be started as soon as possible, preferably within hours after exposure.
-The optimal duration of prophylaxis is unknown and may differ based on institution protocol.
-The most current therapeutic guidelines should be consulted for more information.
-Not approved by US FDA.

Usual Pediatric Dose for HIV Infection:

3 months or older:
3.5 to less than 5 kg: 100 mg orally once a day
5 to less than 7.5 kg: 150 mg orally once a day
7.5 to less than 15 kg: 200 mg orally once a day
15 to less than 20 kg: 250 mg orally once a day
20 to less than 25 kg: 300 mg orally once a day
25 to less than 32.5 kg: 350 mg orally once a day
32.5 to less than 40 kg: 400 mg orally once a day
40 kg or more: 600 mg orally once a day

Use: In combination with other antiretroviral agents, for the treatment of HIV-1 infection

What other drugs will affect efavirenz?

Efavirenz may cause a serious heart problem if you use certain medicines at the same time, including antibiotics, antidepressants, antipsychotic medicines, stomach acid reducers, heart rhythm medicine, and medicines to treat cancer, or malaria. Tell your doctor about all medicines you use, and those you start or stop using during your treatment with efavirenz.

Many drugs can interact with efavirenz. Not all possible interactions are listed here. Tell your doctor about all your current medicines and any you start or stop using, especially:

  • any other HIV or AIDS medications;

  • an antibiotic or antifungal medicine;

  • anti-malaria medicine;

  • cholesterol-lowering medicine;

  • heart or blood pressure medicine;

  • hepatitis C medication;

  • medicine to prevent organ transplant rejection; or

  • seizure medicine.

This list is not complete and many other drugs can interact with efavirenz. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Give a list of all your medicines to any healthcare provider who treats you.

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.