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Efavirenz oral


Oral formulations containing efavirenz.

Drugs List

  • efavirenz 600mg tablets
  • Therapeutic Indications


    HIV infection-combined with other antiretrovirals



    Over 40 kg bodyweight
    600 mg once daily in combination with a nucleoside analogue reverse transcriptase inhibitor with or without a protease inhibitor.

    Under 40 kg bodyweight
    See Dosage; Children


    Children between 3 months and 17 years of age and at least 3.5 kg bodyweight
    In combination with a protease inhibitor and/or nucleoside reverse transcriptase inhibitor, the dose is determined by bodyweight (see below) and given once daily.

    Consider prophylaxis with antihistamines before initiating therapy in children to minimise the incidence of skin rash.

    Capsules (3 months to 17 years of age)
    40 kg and above - 600 mg daily
    32.5 to less than 40 kg - 400 mg daily
    25 to less than 32.5 kg - 350 mg daily
    20 to less than 25 kg - 300 mg daily
    15 to less than 20 kg - 250 mg daily
    7.5 to less than 15 kg - 200 mg daily
    5 to less than 7.5 kg - 150 mg daily
    3.5 to less than 5 kg - 100 mg daily

    Tablets (Adolescents)
    40 kg bodyweight or above - 600 mg daily
    Less than 40 kg bodyweight - not recommended (use capsules)

    Additional Dosage Information

    Co-administration with voriconazole
    The voriconazole maintenance dose should be increased to 400 mg every 12 hours. The efavirenz dose should be halved i.e. to 300 mg once daily.
    When voriconazole therapy is stopped, the initial dose of efavirenz should be restored.

    Co-administration with rifampicin
    The adult dose of efavirenz may be increased to 800 mg per day if rifampicin is given concurrently in patients weighing 50 kg or greater.


    Children under 3 months
    Infants weighing less than 3.5kg
    Congestive cardiac failure with reduced left ventricular ejection fraction
    Long QT syndrome
    Severe bradycardia
    Severe electrolyte imbalance
    Severe hepatic impairment
    Torsade de pointes

    Precautions and Warnings

    Children aged 3 months to 18 years
    Family history of long QT syndrome
    Acute porphyria
    Electrolyte imbalance
    Glucose-galactose malabsorption syndrome
    Hepatitis B
    Hepatitis C
    History of depression
    History of hepatic impairment
    History of psychiatric disorder
    History of seizures
    History of torsade de pointes
    Lactose intolerance
    Mild hepatic impairment
    Severe renal impairment

    Correct electrolyte disorders before treatment
    Treatment does not prevent risk of transmission of HIV
    Advise ability to drive/operate machinery may be affected by side effects
    Consider prophylactic antihistamines for high risk patients
    Not all available products are licensed for all age groups
    Treatment should be initiated by doctor experienced in HIV management
    Some formulations contain lactose
    Advise patient to take at bedtime to reduce adverse effects
    Not to be used as a single agent or added on to a failing regime
    Exclude pregnancy prior to initiation of treatment
    Autoimmune disorders can occur many months after initiation of treatment
    Blood lipid and glucose levels may increase requiring treatment
    Consider monitoring ECG in patients at risk of QT prolongation
    Consider monitoring hepatic enzymes
    Monitor for depressive disorders/suicidal ideation-consider discontinuation
    Monitor patients with hepatic impairment
    Monitor serum electrolytes
    Advise patient to report any new or worsening depression/suicidal ideation
    Advise patient to seek medical advice if joint aches or pain occur
    Advise patient to seek medical advice if movement becomes difficult
    Inflammatory symptoms should be evaluated and treated appropriately
    Risk of developing opportunistic infections
    May affect results of some laboratory tests
    Discontinue if hepatic function deteriorates in pts with hepatic impairment
    Discontinue if severe skin reaction occurs
    Interrupt therapy if hepatic transaminases > 5 times upper limit of normal
    Bioavailability differs with preparations;caution on changing formulations
    Advise patient not to take ginkgo unless advised by clinician
    Advise patient not to take St John's wort concurrently
    Advise patient grapefruit products may increase plasma level
    Female: Two reliable methods of contraception should be used simultaneously

    When any antiretroviral in combination regimen is interrupted due to suspected intolerance, consider also interrupting all antiretroviral medications in order to prevent resistance developing. Restart all medications at the same time when intolerance symptoms have resolved.

    Discontinue efavirenz if severe rash with blistering, desquamation, mucosal involvement or fever occur. If stopping efavirenz consider stopping all antiretrovirals. Mild to moderate rash usually improves with continuation of treatment and antihistamines and/or corticosteroids may be used. Efavirenz is not recommended in patients who have had life-threatening cutaneous reaction e.g. Stevens-Johnson syndrome whilst taking another NNRTI.

    Rash is more common in children; consider prophylaxis with an appropriate antihistamine before initiating treatment.

    Immune reactivation may occur when combination antiretroviral therapy is initiated in HIV infected patients with severe immune deficiency. Inflammatory reactions to asymptomatic or residual opportunistic pathogens may arise. This may lead to aggravation of symptoms or other serious clinical conditions such as cytomegalovirus retinitis, mycobacterial infections or Pneumocystis jiroveci (formerly Pneumocystis carinii) pneumonia. These reactions usually happen in the first few weeks or months after treatment commences and should be evaluated and treated appropriately.

    Blood lipid and glucose levels may increase during antiretroviral therapy. This may be linked to disease control and lifestyle. Refer to established HIV treatment guidelines for monitoring and manage lipid and glucose level disorders as appropriate.

    Patients with chronic hepatitis B or C who are treated with combination antiretroviral therapy have an increased risk of developing severe and potentially fatal hepatic adverse effects, and therefore should be closely monitored during treatment. The product literature relating to concurrent treatments for hepatitis B or C should be consulted.

    Monitor liver enzymes in patients receiving other medications associated with liver toxicity.

    Cases of osteonecrosis have been reported in patients with advanced HIV disease and/or long term exposure to combination antiretroviral therapy, although the aetiology of this condition is thought to be due to several factors including corticosteroid use, alcohol consumption, severe immunosuppression, higher body mass index. Patients should be advised to seek medical advice if they experience joint aches or pains, joint stiffness or difficulty in movement.

    The Drug Database for Acute Porphyria considers efavirenz as probably porphyrinogenic.

    Pregnancy and Lactation


    Use efavirenz with caution in pregnancy. First trimester exposure should be avoided where possible.

    Efavirenz should generally be avoided in pregnancy particularly during the first trimester due to reports of neural tube defects, and given only if no other options are available. Generally guidance states that HIV combination therapy should be continuous to prevent emergence of resistant viral strains, however the US Department of Health and Human Services guidelines recommend avoiding efavirenz in pregnancy particularly during the first trimester due to neural tube defects occurring. Briggs suggests data do not support efavirenz as being a major teratogen. If indicated the drug should not be withheld because of pregnancy.

    There is limited information concerning efavirenz administration during human pregnancy. Post-marketing experience of 206 pregnancies exposed to efavirenz during the first trimester showed no specific malformation patterns. A small number of cases of neural tube defects, including meningomyelocele, have been reported but causality has not been established. The Antiretroviral Pregnancy Registry as of July 2013 reported one neural tube defect in a total of 766 live births from an initial 904 pregnancies. The rates of neural tube defects were reported to be within the general population range.

    Efavirenz has shown teratogenic effects during studies in primates and embryotoxicity has been observed in rats, suggesting a potential for risk in humans. It is not known if efavirenz crosses the placenta however, animal studies and the low molecular weight (about 316) suggest that transfer occurs. Dandy Walker syndrome has also been reported after first trimester exposure.

    Briggs recommends the use of zidovudine during the intrapartum period regardless of current regimen, as this may prevent vertical transmission of HIV to the newborn.

    The use of all medication in pregnancy should be avoided whenever possible; particularly in the first trimester. Non-drug treatments should also be considered. When essential, a medication with the best safety record over time should be chosen, employing the lowest effective dose for the shortest possible time. Polypharmacy should be avoided. Teratogens taken in the pre-embryonic period, often quoted as lasting until 14 to 17 days post-conception, are believed to have an all-or-nothing effect. Where drugs have a short half-life, and when the date of conception is certain, this may allow women to be reassured where drug exposure has occurred within this time frame. Further advice may be available from the UK National Teratology Information Service (NTIS) and through ToxBase, available via password on the internet ( ) or if this is unavailable at the backup site ( ).


    Efavirenz is contraindicated in breastfeeding. It is recommended that HIV infected women should not breastfeed their infants in order to avoid transmission of HIV.

    Insufficient evidence exists for the safety of efavirenz in breastfeeding. The molecular weight (about 316) is low enough that excretion into the breast milk is expected. Due to insufficient data, risk to the infant cannot be excluded.

    Studies in lactating rats demonstrated that efavirenz is excreted in milk achieving much higher concentrations than in the maternal plasma.

    Neonates, infants born prematurely, those with low birth weight, those with an unstable gastrointestinal function or who have serious illnesses may require special consideration. For any infant, if a drug is prescribed to the nursing mother, it should be at the lowest practical dose and for the shortest time. When drug administration is unavoidable and breastfeeding is to continue, minimisation of exposure of the infant to the drug may sometimes be achieved by timing the maternal doses to just after a feeding episode. Infants exposed to drugs via breast milk should be monitored for unusual signs or symptoms. Interactions between the drug received by the infant from the mother's milk and medication prescribed for the infant should also be considered, for example, when the drug given to the infant may prevent metabolism of the drug received via breast milk.
    Specialist advice is available from the UK Drugs in Lactation Advisory Service at


    Advise patients to take the daily dose at bedtime to improve the tolerability of nervous system symptoms.

    Advise patients to take on an empty stomach to prevent adverse reactions occurring. When administered with food, increased plasma levels of efavirenz are observed and this may lead to an increased incidence of adverse effects.

    Capsule contents may be administered with a small amount of food (1 to 2 teaspoons). Patients and carers should be instructed to open the capsule carefully to avoid spillage or dispersion of the capsule contents into the air. It is recommended to hold the capsule vertically with the cap facing upwards and to pull the cap away from the body of the capsule and to mix the contents with food in a small container. The mixture should then be administered as soon as possible (within 30 minutes of mixing). Following administration, a small amount (2 teaspoons) of food should be added to the mixing container and stirred to disperse any remaining drug residue and this must also be given to the patient. No additional food is to be consumed within 2 hours of administration.

    Advise patient to avoid grapefruit products.

    Advise patient to avoid St John's Wort.

    Advise patient to avoid ginkgo unless advised by clinician.

    Advise patient to report any new or worsening depression or suicidal ideation.

    Advise patient to seek medical advice if joint aches or pains occur or if movement becomes difficult.

    Inform patients nervous system symptoms involving CNS depression are reported frequently. These tend to start in the first two days of treatment and resolve after the first 2 to 4 weeks. These are not predictive of the less frequent psychiatric symptoms.

    Advise patient their ability to drive and operate machinery may be affected by the side effects.

    Side Effects

    Abdominal pain
    Abnormal thinking
    Attention disturbances
    Autoimmune hepatitis
    Blurred vision
    Cerebellar dysfunction
    Dream abnormalities
    Elevated amylase levels
    Emotional lability
    Erythema multiforme
    Gamma glutamyl transferase (GGT) increased
    Graves' disease
    Hepatic failure
    Hypersensitivity reactions
    Immune Reactivation/Reconstitution Syndrome
    Impaired co-ordination
    Impaired concentration
    Increase in serum ALT/AST
    Maculopapular rash
    Metabolic disorders
    Nervous system effects
    Photoallergic reactions
    Psychiatric disorders
    Psychosis-like reactions
    Sleep disturbances
    Stevens-Johnson syndrome
    Suicidal tendencies

    Effects on Laboratory Tests

    Cannabinoid test interaction
    Efavirenz does not bind to cannabinoid receptors. False-positive urine cannabinoid test results have been reported with some screening assays in uninfected and HIV-infected volunteers who received efavirenz. The manufacturers suggest confirmatory testing by a more specific method such as gas chromatography/mass spectrometry should be used in such cases.


    It is strongly recommended that the UK National Poisons Information Service be consulted on cases of suspected or actual overdose where there is doubt over the degree of risk or about appropriate management.

    The following number will direct the caller to the relevant local centre (0844) 892 0111

    Information may be obtained if you have access to ToxBase the primary clinical toxicology database of the National Poisons Information Service. This is available via password on the internet ( ) or if this is unavailable at the backup site ( ).

    Further Information

    Last Full Review Date: December 2015

    Reference Sources

    Drugs During Pregnancy and Lactation: Treatment Options and Risk Assessment, 2nd edition (2007) ed. Schaefer, C., Peters, P. and Miller, R. Elsevier, London.

    Drugs in Pregnancy and Lactation: A Reference Guide to Fetal and Neonatal Risk, 9th edition (2011) ed. Briggs, G., Freeman, R. and Yaffe, S. Lippincott Williams & Wilkins, Philadelphia.

    Joint Formulary Committee. British National Formulary (online) London: BMJ Group and Pharmaceutical Press [Accessed on April 11, 2014].

    Paediatric Formulary Committee. BNF for Children (online) London: BMJ Group, Pharmaceutical Press, and RCPCH Publications [Accessed on April 11, 2014].

    Summary of Product Characteristics: Sustiva 50mg, 100mg and 200mg Hard Capsules. Bristol Myers Squibb. Revised October 2018.
    Summary of Product Characteristics: Sustiva 600mg Film-Coated Tablets. Bristol Myers Squibb. Revised October 2018.

    The Drug Database for Acute Porphyria (NAPOS)
    Available at:
    Efavirenz. Last revised: July 2 2015
    Last accessed: December 17 2015

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