January 4, 2014
Fact Sheet 475).
Efavirenz is a non-nucleoside reverse transcriptase inhibitor (a "non-nuke" or NNRTI). These drugs stop HIV from multiplying by preventing the reverse transcriptase enzyme from working. This enzyme changes HIV's genetic material (RNA) into the form of DNA. This step has to occur before HIV's genetic code gets inserted into an infected cell's genetic codes.
There are no absolute rules about when to start ART. You and your health care provider should consider your CD4 cell count, your viral load, any symptoms you are having, and your attitude about taking HIV medications. Fact Sheet 404 has more information about guidelines for the use of ARVs.
If you take efavirenz with other ARVs, you can reduce your viral load to extremely low levels, and increase your CD4 cell counts. This should mean staying healthier longer.
Efavirenz seems to get into the central nervous system (spinal fluid). It may help prevent mental problems such as dementia.
Fact Sheet 126 for more information on resistance.
Sometimes, if your virus develops resistance to one drug, it will also have resistance to other ARVs. This is called "cross-resistance." Cross-resistance among NNRTIs develops very easily. If you develop resistance to one NNRTI, you probably won't be able to use any of them in your ART.
Resistance can develop quickly. It is very important to take ARVs according to instructions, on schedule, and not to skip or reduce doses.
It is recommended that you take efavirenz on an empty stomach, at bedtime. This dosing should result in the fewest side effects. High-fat foods increase efavirenz levels and should be avoided before taking a dose.
The most common side effects are fatigue (see Fact Sheet 551), rash, nausea, dizziness, diarrhea, headache and insomnia. Taking efavirenz with food increases drug levels and may increase side effects. Some people see changes in body fat (see Fact Sheet 553).
To avoid dizziness after taking efavirenz, take it before you go to sleep. Some people have vivid dreams. For most people, these side effects disappear within the first two weeks.
About 5% of patients taking efavirenz had serious psychiatric symptoms. If you are taking efavirenz and experience serious depression or other psychiatric symptoms, talk to your health care provider right away.
There have been a few reports of serious liver problems, even in people with no previous liver disease. Liver function tests should be done regularly, especially for patients who have had hepatitis B or C or other liver problems.
Studies in monkeys showed that efavirenz is likely to cause birth defects. Pregnant women should not take it, especially during the first 3 months of pregnancy. However, recent studies have shown no increase in birth defects in pregnant women taking efavirenz.
People who take efavirenz may falsely test positive for use of marijuana or benzodiazepines, tranquilizers like Xanax, Valium or Librium. To prove that the results are false, you would have to identify the drug that you are taking. This would mean disclosing that you have HIV infection.
Drugs to watch out for include other ARVs, drugs to treat tuberculosis (see Fact Sheet 518), especially rifampin, which may require that you take a higher dose of efavirenz. Other drugs to watch out for include medications for erectile dysfunction (such as Viagra), for heart rhythm (antiarrhythmics), or angina and for migraine headaches. Interactions are also possible with several antihistamines (allergy medications), sedatives, drugs to lower cholesterol or blood pressure, and anti-fungal drugs. Make sure that your health care provider knows about ALL drugs and supplements you are taking.
Efavirenz decreases blood levels of methadone. Efavirenz can lower concentrations of buprenorphine.
The herb St. John's Wort (See Fact Sheet 729) lowers the blood levels of some nonnucleoside reverse transcriptase inhibitors. Do not take it with efavirenz.