Efavirenz - How to use | Side effects

This article was medically reviewed by M.Pharm, Marko Tanaskovic on August 12, 2018. To read more about an author, click here.

Efavirenz is a medicine from the group of antiretroviral drugs and works by inhibiting reverse transcriptase of HIV-1, and is therefore indicated for the treatment of HIV-1 infection. Efavirenz is used only in combination with other drugs.

Precautions and Interactions

Use of Efavirenz is contraindicated in the following conditions:

  • Severe hepatic impairment. There have been reports of severe hepatic impairment induced by this drug.1 It is necessary to carefully monitor liver function while you are on treatment with this drug. If you notice symptoms of liver damage (nausea, pain in the right upper abdomen or jaundice) you should contact your doctor.

Co-administration with the following drugs is contraindicated:

  • Benzodiazepines, such as:
    • alprazolam
    • midazolam
    • bromazepam
    • lorazepam and others
    Concomitant administration with these drugs increases the risk of side effects, such as: respiratory depression (shortness of breath) and increased need for sleep.
  • Cisapride (a drug used for the treatment of gastroesophageal reflux disease). Efavirenz increases the concentration of cisapride in the blood which leads to the occurrence of side effects
  • Opioid analgesics, such as:
    • fentanyl
    • oxycodone
    Efavirenz decreases effects of these drugs and increases the risk of withdrawal symptoms.

Co-administration with the following drugs is also contraindicated because it increases the risk of serious arrhythmias:

  • Bepridil - calcium channel blocker used to treat angina
  • New generation antihistamines such as: astemizole and terfenadine
  • Tetracyclic antidepressants (e.g. trazodone)
  • Tricyclic antidepressants, such as: imipramine and desipramine
  • Drugs used for the treatment of emesis induced by chemotherapy (e.g. ondansetron)
  • Pimozide - antipsychotic
  • Oxaliplatin - a drug used for the treatment of colon cancer
  • Osimertinib - a drug used for the treatment of non-small-cell lung cancer (NSCLC)
  • Chlorpromazine - antipsychotic
  • Antiarrhythmic drugs, such as: amiodarone and disopyramide
  • Antifungal drugs such as ketoconazole and voriconazole
  • Fluoroquinolone antibiotics, such as:
    • ciprofloxacin
    • spartfloksacin
    • moxifloxacin
    • norfloxacin
    • trovafloxacin
  • Ketolide and macrolide antibiotics, such as: telithromycin and erythromycin
  • Ergot derivatives (e.g. ergotamine) - used for the treatment of migraine
  • St. John's Wort
  • Nightshade (belladonna)

Keep in mind that taking this medication does not mean the virus is gone and you cannot infect other people.

Efavirenz should be administered with caution in patients:

  • Who have or have had a mental illness. Such patients are at an increased risk of suicidal thoughts. If you notice suicidal thoughts, contact your doctor immediately.
  • Who suffer from epilepsy and are being treated with drugs (carbamazepine and phenytoin). Manufacturer states that it is necessary to first check the concentration of these drugs in the blood before starting Efavirenz.

Tell your doctor if you notice lump anywhere on your body, because it may be a sign of lipoma because Efavirenz causes a redistribution of body fat.

If you notice hip pain, knee pain or shoulder pain, contact your doctor, because these are the signs of osteonecrosis (necrosis of bone tissue).

Efavirenz, pregnancy and breastfeeding

Manufacturer states that women should avoid becoming pregnant during the treatment and for three months after the treatment with because serious defects were identified in newborns whose mothers took this medicine during pregnancy. WHO states on the basis of recommendation British HIV Association that Efavirenz should not be avoided during pregnancy because it belongs to the highly effective drugs with relatively good tolerability.2

Breastfeeding should be avoided while on this drug.

How to use

Efavirenz should be taken on an empty stomach, in the evening, just before bedtime. Taking this drug with food results in an increase of Efavirenz concentration in the blood and thus lead to the side effects.

Taking the pill in the evening, just before bedtime, improves the tolerability of central nervous system side effects.

Efavirenz is used in combination with other drugs at a dose of 600 mg once a day.

It can be used in children older than 3 years and the dose is determined based on body weight, as given in the table below:

Body weight (lb) Recommended dose
28.65 - 33.07 200 mg once a day
33.07 - 44.1 250 mg once a day
44.1 - 55.1 300 mg once a day
55.1 - 71.6 350 mg once a day
71.6 - 88.2 400 mg once a day
>= 88.2 600 mg once a day

Side effects

Efavirenz may cause the following side effects:

  • Nausea
  • Diarrhea
  • Stomach pain
  • Rash
  • Increased blood cholesterol and triglycerides levels
  • Fainting
  • Headache
  • Nightmares
  • Osteonecrosis (pain and stiffness in the joints)
  • Vertigo
  • Depressed mood
  • Gynecomastia
  • Suicidal thoughts
  • Seizures
  • Loss of coordination
  • Liver damage


  1. NCBI link 1
  2. WHO

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