Fact Sheet Number 432
- WHAT IS EFAVIRENZ?
- WHO SHOULD TAKE IT?
- WHAT ABOUT DRUG RESISTANCE?
- HOW IS IT TAKEN?
- WHAT ARE THE SIDE EFFECTS?
- HOW DOES IT REACT WITH OTHER DRUGS?
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PrintEfavirenz is a drug used for antiviral
therapy. It is also called Sustiva®. It is manufactured
by Bristol-Myers Squibb.
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.
IT?
Efavirenz was approved as an antiviral drug for people with HIV
infection. There are no absolute rules about when to start antiviral
drugs. You and your doctor should consider your T-cell count,
your viral load, any symptoms you are having, and your attitude
about taking HIV medications. Fact
Sheet 411 has more information about guidelines
for the use of antiviral medications.
If you take efavirenz with other antiviral drugs, you can reduce
your viral load to extremely low levels, and increase your T-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.
RESISTANCE?
Many new copies of HIV are mutations. They are slightly different
from the original virus. Some mutations can keep multiplying
even when you are taking an antiviral drug. When this happens,
the drug will stop working. This is called “developing resistance”
to the drug. See Fact Sheet 414
for more information on resistance.
Sometimes, if your virus develops resistance to one drug, it
will also have resistance to other antiviral drugs. 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 antiviral therapy.
Resistance can develop quickly. It is very important to
take antiviral medications according to instructions, on schedule,
and not to skip or reduce doses.
Efavirenz is taken by mouth as a capsule. The normal adult dose
is 600 milligrams (mg) once a day at bedtime. Efavirenz is available
in capsules of 50 mg, 100 mg, and 200 mg. Most adults will take
3 of the 200 mg capsules at a time. A 600 mg tablet of efavirenz
was approved in early 2002.
It is recommended that you take efavirenz on an empty stomach,
at bedtime. This dosing should result in the fewest side effects.
EFFECTS?
When you start any antiviral treatment, you may have temporary
side effects such as headaches, high blood pressure, or just feeling
ill. These side effects usually get better or disappear over time.
The most common side effects of Efavirenz are rash, nausea,
dizziness, diarrhea, headache and insomnia. Taking efavirenz with
food increases drug levels and may increase side effects. To avoid
dizziness after taking Efavirenz, take it before you go to sleep.
Some people have vivid dreams when taking Efavirenz. For most
people, these side effects disappear within the first two weeks.
Studies in monkeys showed that Efavirenz is likely to cause
birth defects. Pregnant women should not take it.
People who take Efavirenz may falsely test positive for marijuana
use. 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.
WITH OTHER DRUGS?
Efavirenz is broken down by the liver and can interact with other
drugs that also use the liver. Combining these drugs can change
the amount of each drug in your bloodstream and cause an under-
or overdose. Drugs to watch out for include several antihistamines,
sedatives, and anti-fungal drugs. Make sure that your doctor knows
about ALL drugs you are taking.
- Efavirenz lowers blood levels of most protease inhibitors.
Your doctor will need to increase your dosage of indinavir
or amprenavir. Efavirenz and
saquinavir should not be used
together.
- Efavirenz decreases blood levels of methadone. People using
both drugs will need to increase their dosage of methadone.
Revised February 7, 2002
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New Mexico AIDS Education and Training Center
and the New Mexico Department of Health