An HIV antiretroviral (NNRTI)
Efavirenz
An HIV antiretroviral that blocks the virus from copying itself, always used as part of a combination.
What is Efavirenz?
Efavirenz is a non-nucleoside reverse transcriptase inhibitor (NNRTI) used to treat HIV. It is always taken alongside other antiretrovirals as part of combination therapy that keeps the virus under control. It is usually taken at bedtime on an empty stomach because it can cause vivid dreams, dizziness and mood changes.
Education and reference only. This is a plain-language guide to Efavirenz — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Efavirenz is a non-nucleoside reverse transcriptase inhibitor (NNRTI), one of the medicines used to treat HIV infection. It is never used on its own; it forms part of a combination of antiretrovirals that together suppress the virus. In the UK it has largely been replaced by newer agents but is still used in some regimens, including settings where it has a long track record.
How it works
HIV needs an enzyme called reverse transcriptase to turn its genetic material into a form it can insert into human cells. Efavirenz attaches directly to this enzyme and stops it working, so the virus cannot copy itself. When combined with other antiretrovirals that block the virus in different ways, the amount of HIV in the blood falls to very low levels and the immune system can recover.
Company & origin
Originated / developed by: Originally developed by DuPont and later marketed by Bristol-Myers Squibb; widely available as a generic medicine..
Developed in the United States in the 1990s and approved as one of the first non-nucleoside reverse transcriptase inhibitors for HIV.
Practical use
How to take Efavirenz
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take it every day at the same time, ideally at bedtime, to help with side effects.
- Take it on an empty stomach, as food can increase the amount absorbed and worsen side effects.
- Swallow it with a drink of water, alongside the other antiretrovirals in your regimen.
- Try not to miss doses, as good adherence prevents the virus becoming resistant.
- If you miss a dose, take it when you remember unless your next dose is near, then skip it; never double up.
- Do not stop without speaking to your HIV team, even if you feel well.
Weighing it up
Advantages & disadvantages of Efavirenz
Advantages
- Effectively suppresses HIV when combined with other antiretrovirals, helping the immune system recover.
- Taken once a day, which makes a regimen simpler to follow.
- Long experience of use, including some settings in pregnancy, and available as a generic medicine.
Disadvantages
- Often causes vivid dreams, dizziness and difficulty concentrating, especially early on.
- Can affect mood and has been linked to depression, so needs careful monitoring.
- Interacts with many medicines and has been overtaken by better-tolerated newer options.
Practical use
Good to know
Efavirenz keeps HIV under control but does not cure it, so it must be taken every day exactly as prescribed; missing doses lets the virus become resistant. It is usually taken at bedtime on an empty stomach to reduce side effects. Vivid dreams, dizziness, difficulty concentrating and low mood are common in the first weeks and often settle. Tell your team about any new or worsening mood changes.
Who should not take it / use with caution
- People who have had a serious allergic reaction to efavirenz.
- People with a history of severe depression or other serious mental-health problems, unless carefully assessed.
- People with significant liver disease, without specialist advice.
Monitoring
- The amount of HIV in the blood (viral load) and the immune-cell (CD4) count.
- Mood and mental health, particularly in the first weeks.
- Liver function and cholesterol from time to time.
Side effects
- Vivid or disturbing dreams and trouble sleeping.
- Dizziness, light-headedness or difficulty concentrating.
- Low mood, anxiety or other changes in mood.
- Rash — usually mild, but seek advice urgently for any blistering, peeling, or rash with fever or mouth sores.
Key interactions
- St John's wort, which can reduce its effectiveness and is not recommended.
- Some other antiretrovirals, antifungals, anti-seizure medicines and rifampicin.
- Hormonal contraception may be less reliable, so additional precautions are advised.
Available as: Available as tablets and capsules, including fixed-dose combination tablets.
Answers
Efavirenz: frequently asked questions
Does efavirenz cure HIV?
No. It keeps the virus under control as part of combination therapy, but it does not get rid of HIV. You need to keep taking your full regimen every day for it to keep working.
Why is it taken at bedtime?
It can cause dizziness, vivid dreams and difficulty concentrating. Taking it at bedtime means you sleep through the worst of these effects, which usually ease over the first few weeks.
Why on an empty stomach?
Taking it with food, especially a fatty meal, increases how much is absorbed and can make side effects worse, so it is usually taken without food.
What if it affects my mood?
Tell your HIV team straight away if you feel low, anxious or have any distressing thoughts. Mood changes are a recognised effect and your regimen can often be adjusted.
Why must I take it every day?
Missing doses lets HIV multiply and become resistant, which can make the medicine stop working. Good daily adherence keeps the virus suppressed and protects your future options.
The wider class
About Antiretrovirals (HIV)
Efavirenz belongs to the antiretrovirals (hiv) class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
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Authoritative sources
- BNF
- NICE CKS
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