References UK clinical guidance from the NHS, the British HIV Association (BHIVA), and the British Association for Sexual Health and HIV (BASHH). Last updated: April 2026.
Efavirenz (brand name Sustiva, also part of the combination Atripla) is a non-nucleoside reverse transcriptase inhibitor (NNRTI) that was one of the most widely used HIV drugs for over a decade. It’s being replaced by newer drugs in most UK guidelines, but is still used globally and in some UK patients who have been stable on it for years.
Here’s what efavirenz does and what makes it notable.
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How Efavirenz Works
Like other NNRTIs, efavirenz blocks HIV’s reverse transcriptase enzyme directly, preventing the virus from converting its RNA into DNA. It’s taken once daily, usually at bedtime.
Why Efavirenz Is Notable
Efavirenz is best known for its neuropsychiatric side effects, which set it apart from most other HIV drugs:
| Side Effect | How Common | When It Happens |
|---|---|---|
| Vivid dreams and nightmares | Very common | First few weeks, often persists |
| Dizziness | Common | First few weeks |
| Difficulty concentrating | Common | Variable |
| Mood changes, depression | Moderate | Can develop over time |
| Anxiety | Moderate | Variable |
| Suicidal thoughts (rare but serious) | Uncommon | Report immediately |
| Rash | Common | First few weeks |
Taking efavirenz at bedtime on an empty stomach can reduce the impact of dizziness and drowsiness.
When Is Efavirenz Still Used?
- In people who have been stable on it for years without side effects
- In some low and middle income country settings where it remains first-line
- When newer drugs aren’t available or suitable
In the UK, dolutegravir and bictegravir-based regimens are now preferred for most people starting treatment.
Drug Interactions
Efavirenz is a moderate CYP3A4 inducer, meaning it speeds up the breakdown of some other drugs. Notable interactions include:
- Some hormonal contraceptives — may be less effective
- Methadone — may need dose increase
- Some statins — dose adjustments needed
- Rifampicin — can be used together but with dose adjustment
Switching from Efavirenz
If you’re on efavirenz and experiencing side effects, talk to your HIV team about switching. Common switches include moving to dolutegravir, bictegravir or rilpivirine-based regimens. Most people notice improvements in sleep, mood and concentration after switching.
Read more: Nevirapine | Biktarvy | What is HIV?
Frequently Asked Questions
Should I switch from efavirenz?
If you’re doing well on efavirenz without side effects, there’s no urgent need to switch. But if you have neuropsychiatric symptoms, modern alternatives are better tolerated.
Will the vivid dreams stop?
Some people adapt over weeks or months. For others, vivid dreams persist for as long as they take the drug. Switching usually resolves them.
Can efavirenz cause a positive drug test?
Efavirenz has been reported to cause false-positive results on some cannabinoid (THC) screening tests. If this happens, a confirmatory test will show it’s a false positive.
Related reading
- Eviplera: How This Anti-HIV Drug Works
- Dolutegravir: A Complete Guide to This HIV Medication
- Understanding Efavirenz in HIV Treatment
- Injectable HIV Treatment: Everything You Need to Know
- Are HIV Tests Accurate If You're on PrEP, PEP or ART?
Sources
- NHS — Sexual health conditions
- BASHH — UK clinical guidelines for STI management
- British HIV Association (BHIVA) — HIV treatment guidelines
- Terrence Higgins Trust — sexual health information
- UK Health Security Agency — STI surveillance data
Steve Page is a recognised expert on Sexually Transmitted Diseases (STDs) and STD treatments, having published numerous articles in peer-reviewed journals and presented his research at conferences around the world. He has an in-depth understanding of the latest medical research on STDs, and is an advocate for the development of new treatments and protocols to improve the health of those affected. In addition to his research, he has dedicated his career to understanding the causes and symptoms of STDs, as well as how to best treat those impacted.
