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# Efavirenz

A once-daily NNRTI used for years as first-line treatment. Typical effects are dizziness, vivid dreams and psychiatric symptoms.

Updated 2026-11-01

- Class: [Non-nucleoside reverse transcriptase inhibitors (NNRTIs)](https://durgical.com/en/pharmacology/classes/non-nucleoside-reverse-transcriptase-inhibitors/)
- Enzyme: HIV-1 reverse transcriptase (NNRTI pocket)
- ATC code: J05AG03
- WHO Model List of Essential Medicines

Also called: EFV

✂**HIV-1 reverse transcriptase (NNRTI pocket)**Efavirenz

ⓘ The figure shows efavirenz in the allosteric pocket of HIV-1 reverse transcriptase.

**Target in 3D:** HIV-1 reverse transcriptase (NNRTI pocket). PDB structure 1FK9 (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/1FK9) · Drag to rotate · pinch to zoom

## Mechanism of action

It binds the hydrophobic pocket of the p66 subunit of HIV-1 reverse transcriptase, away from the active site, leaving the enzyme stiff and twisted so it stops copying viral RNA into DNA. It needs no phosphorylation. A single mutation (such as K103N) is enough to lose its effect.

- It binds the allosteric pocket of reverse transcriptase
- It distorts the enzyme without competing with nucleotides
- Copying of viral RNA into DNA stops

## Pharmacokinetics

**Metabolism**
Liver, mainly by CYP2B6; it induces CYP3A and CYP2B6, including its own clearance

**Half-life**
Long: about 40 to 55 hours at steady state

## Indications

- HIV-1 infection, combined with other antiretrovirals (now an alternative to dolutegravir regimens) [HIV infection and AIDS →](https://durgical.com/en/conditions/hiv-infection-and-aids/)

## Adverse effects

### Common

- Dizziness, insomnia, vivid dreams, poor concentration (usually settle within weeks)
- Rash in the first weeks
- Raised lipids

### Serious (rare, important)

- Severe psychiatric symptoms: depression, suicidal thoughts, psychosis
- Late neurotoxicity (ataxia, encephalopathy), sometimes linked to CYP2B6 variants
- Hepatotoxicity
- QTc prolongation

## Contraindications

- Previous severe hypersensitivity (Stevens-Johnson, erythema multiforme)
- Use with elbasvir/grazoprevir

## Key interactions

**Drugs metabolised by CYP3A or CYP2B6**
Efavirenz induces these enzymes and can lower their levels

**Hormonal contraceptives**
They can lose efficacy: a barrier method is added

**Voriconazole**
Two-way interaction requiring adjustment of both drugs

## What is monitored

- Mood and psychiatric symptoms
- Liver tests
- Lipids
- Pregnancy test before starting in women of childbearing potential

## Administration and safety

- By mouth, on an empty stomach and preferably at bedtime, to tolerate nervous system symptoms better
- It can give a false positive on some urine cannabinoid tests

## Nursing care

- Warn that dizziness and vivid dreams are common at first and usually settle
- Ask about depression or suicidal thoughts and refer at once
- Teach to avoid hazardous tasks while dizzy
- Advise added barrier contraception

## Pregnancy and breastfeeding

There are retrospective reports of neural tube defects after first-trimester exposure; effective contraception is advised during treatment and for weeks afterwards because of its long half-life.

## Memory aid

'EFavirenz: Eerie dreams, Feelings down': vivid dreams and depression.

## Test yourself

Think of the answer, then tap the question to see it.

## What are efavirenz's most typical adverse effects?

Nervous system effects: dizziness, insomnia, vivid dreams and sometimes severe psychiatric symptoms.

## Why is it given at bedtime?

So the nervous system symptoms, strongest after the dose, fall during sleep and are better tolerated.

## What does efavirenz do to hormonal contraceptives?

By inducing cytochrome enzymes it can reduce their efficacy; a barrier method is added.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/efavirenz/)

## Related drugs

- [Nevirapine](https://durgical.com/en/pharmacology/nevirapine/)
- [Rilpivirine](https://durgical.com/en/pharmacology/rilpivirine/)
- [Doravirine](https://durgical.com/en/pharmacology/doravirine/)

## Related conditions

- [HIV infection and AIDS](https://durgical.com/en/conditions/hiv-infection-and-aids/)

[← Back to the class: Non-nucleoside reverse transcriptase inhibitors (NNRTIs)](https://durgical.com/en/pharmacology/classes/non-nucleoside-reverse-transcriptase-inhibitors/)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [DailyMed - EFAVIRENZ tablet, film coated](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=92603fa5-7a2c-4bfb-9a70-aadb4fba952c) (DailyMed (U.S. National Library of Medicine), 2024); [Efavirenz: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a699004.html) (MedlinePlus (U.S. National Library of Medicine), 2025); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=J05AG03) (WHO Collaborating Centre for Drug Statistics Methodology, 2026); [WHO recommends dolutegravir as preferred HIV treatment option in all populations](https://www.who.int/news/item/22-07-2019-who-recommends-dolutegravir-as-preferred-hiv-treatment-option-in-all-populations) (World Health Organization, 2019).

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Representative model, for educational purposes only.

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