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What does it do?

Efavirenz is used with other medicines to control HIV.

Before you start

  • Tell your doctor if you have liver or mental health problems.
  • Tell your doctor if you are pregnant, planning to become pregnant, or breastfeeding.

How should you take it?

Take efavirenz as directed, usually at night time. It is very important to take it regularly. If you often forget to take efavirenz, it may not work as well.
Take the tablets with a glass of water.
Measure the liquid carefully with an oral syringe or measuring spoon.

What if you forget a dose?

If it is nearly time for your next dose, skip the missed dose and take your next dose at the usual time. Otherwise, take the missed dose as soon as you remember. Do not take two doses at the same time.

Can you take other medicines?

Efavirenz can react with many medicines, sometimes with severe results.
Tell your pharmacist or doctor about all medicines or treatments that you may be taking including vitamins, herbal products, or recreational drugs.

What side effects might you notice?

Side EffectsRecommended action

Severe skin rash, skin peeling or blisters

Stop taking and see your doctor immediately

Symptoms of liver problems including: yellow skin or eyes, itching, dark urine, pale bowel motions, abdominal pain

Suicidal thoughts

Tell your doctor immediately

Unusual behaviour or thinking, low mood, nervousness, anxiety

Tell your doctor

Stomach upset

Tell your doctor if troublesome

Drowsiness, dizziness, trouble concentrating, tiredness or weakness, headache

Trouble sleeping, strange dreams

Common when you first start but should improve in a few weeks. Taking at night may help. If these continue or are severe, tell your doctor.

Skin rash

This can occur in the first few weeks. Rarely, this may be serious. Ring your clinic to check

If you notice any other effects, discuss them with your doctor or pharmacist.

Other information:

  • You will need regular blood tests while taking efavirenz to check if it is causing problems with your liver. You will also need blood tests to check your viral load.
  • Efavirenz can impair your ability to do tasks such as driving or using machines. Alcohol makes this worse. Discuss your risk with your health professional. (search NZTA - Are you safe to drive?)
  • Grapefruit, grapefruit juice or sour/Seville oranges may react with efavirenz. Discuss with your pharmacist.
  • As your HIV comes under control, your immune system begins to recover. It may start fighting infections better than before which may make you unwell for a while. Your doctor may call this Immune Reconstitution Syndrome.
  • Treatment for HIV may change your body shape. These changes can include fat build-up, fat loss, or both. Discuss this with your doctor.
  • Do not stop taking efavirenz without talking to your doctor first.
  • Efavirenz liquid expires 30 days after you first open the bottle. If you have any liquid leftover after 30 days, take it back to your pharmacy.

This leaflet contains important, but not all, information about this medicine.

Prepared by the MyMedicines Committee at Christchurch Hospital, Te Whatu Ora - Waitaha, New Zealand. March 2023

For more general information about this sheet and its contents, see: What does a My Medicines sheet cover?

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About My Medicines

My Medicines Patient Information Leaflets (PILs) contain important, but not all, information about the medicines they describe.

For more information about the sheets, see: What does a My Medicines sheet cover?

My Medicines is developed by a team at Te Whatu Ora – Waitaha. Our team is made up of doctors, pharmacists, and a non-medical person to help us keep to plain language. We also discuss our information with specialist health professionals or groups when needed