Efavirenz an antiretroviral | NNRTI

Efavirenz is an antiretroviral (anti-HIV) drug that is part of the non-nucleoside reverse transcriptase inhibitor (NNRTIs or Non Nukes) family. It is used together with other antiretrovirals to delay the progression of HIV infection. By doing this, your immune system should improve (increase in CD4+ count) and you will be better protected against infections.
Efavirenz is a benzoxamine compound.

Efavirenz does not cure AIDS or completely kill the HIV virus, but helps to prevent further damage by slowing down the production of new viruses. Treatment with efavirenz does not reduce the risk of passing infection on to others. You will still be able to pass HIV by sexual contact, by blood transfer or by sharing needles. You should always use appropriate precautions to prevent passing HIV on to others.

Class: Efavirenz is a benzoxamine compound.

Antiviral Activity: Non-nucleoside reverse transcriptase inhibitors (NNRTIs) are highly selective for HIV-1 but do not exhibit activity against other viruses.

Mechanism of Action

NNRTIs bind noncompetitively to an active site of the reverse transcriptase molecule. Reverse transcriptase directs the polymerization of DNA from viral RNA. The NNRTIs inhibit this polymerization by altering the position of critical amino acids within the catalytic site.


The in vitro 90% inhibitory concentration of efavirenz for HIV-1 ranges from 1.7 to 25 nM. After adjustment for protein binding, these inhibitory concentrations range between 0.34 to 5 μM.


Efavirenz is well absorbed after oral administration and peak efavirenz concentrations are attained by 5 hours after dosing. Steady-state plasma concentrations are reached in 6-10 days. Increases in AUC and Cmax are seen with the administration of efavirenz with a high- fat meal (above 54 g fat) and should be avoided. Efavirenz is approximately 99% plasma protein bound.
At standard adult doses, efavirenz exhibits linear pharmacokinetics. Efavirenz is principally metabolized by CYP450 2B6 and 3A4 to hydroxylated metabolites with subsequent glucuronidation. Efavirenz is an inducer and an inhibitor of the cytochrome P450 system and leads to self-induction.


The Food and Drug Administration (FDA) cautions that efavirenz should not be used in the first trimester of pregnancy because of the potential risk of neural tube defects, which have been observed among children exposed to efavirenz in utero and in animal studies.
Efavirenz is not recommended for children under the age of 3 months or weighing less than 3.5 kg because it has not been adequately studied in these patients.
Taking Efavirenz on an empty stomach, may reduce the undesirable effects. Grapefruit juice should be avoided when taking this medicine.


Serious birth defects have been seen in unborn animals and in the babies of women treated with efavirenz or a combination medicine containing efavirenz, emtricitabine and tenofovir during pregnancy. If you have taken efavirenz or the combination tablet containing efavirenz, emtricitabine, and tenofovir during your pregnancy, your doctor may request regular blood tests and other diagnostic tests to monitor the development of your child.
You should not breast feed your baby if you are taking Efavirenz.

Driving and using machines

Efavirenz may cause dizziness, impaired concentration, and drowsiness. If you are affected, do not drive and do not use any tools or machines.

Efavirenz contains lactose and sodium

If you have been told by your doctor that you have an intolerance to some sugars contact your doctor before taking this medicine.
This medicine contains less than 1 mmol sodium (23 mg) per tablet, that is to say essentially ‘sodium-free’.

How to take Efavirenz

Always take this medicine exactly as your doctor or pharmacist has told you. It is recommended that the tablet be swallowed whole with water. Check with your doctor or pharmacist if you are not sure. Your doctor will give you instructions for proper dosing.
• The recommended dose for adults is 600 mg once daily.
• The dose for Efavirenz may need to be increased or decreased if you are also taking certain medicines
• Efavirenz is for oral use. Efavirenz is recommended to be taken on an empty stomach preferably at bedtime. This may make some side effects (for example, dizziness, and drowsiness) less troublesome. An empty stomach is commonly defined as 1 hour before or 2 hours after a meal.
• It is recommended that the tablet be swallowed whole with water
• Efavirenz must be taken every day.
• Efavirenz should never be used alone to treat HIV. Efavirenz must always be taken in combination with other anti-HIV medicines.

Use in children and adolescents

• Efavirenz film-coated tablets are not suitable for children weighing less than 40 kg.
• The dose for children weighing 40 kg or more is 600 mg once daily.

Side effects

The nervous system symptoms tend to occur when treatment is first started, but generally decrease in the first few weeks. In one study, nervous system symptoms often occurred during the first 1-3 hours after taking a dose. If you are affected your doctor may suggest that you take Efavirenz at bedtime and on an empty stomach. Some patients have more serious symptoms that may affect mood or the ability to think clearly. Some patients have actually committed suicide. These problems tend to occur more often in those who have a history of mental illness. Always notify your doctor immediately if you have these symptoms or any side effects while taking Efavirenz.

• serious allergic reaction that may cause shortness of breath, wheezing or difficulty breathing; swelling of the face, lips, tongue or other parts of the body; rash, itching or hives on the skin

• severe skin reactions which may cause red (moist), itchy and irregular spots similar to the rash of measles or widespread rash with blisters and peeling skin, particularly around the mouth, nose, eyes and genitals. The spots may progress to form raised, red, pale-centered marks. Those affected may have fever, sore throat, headache and/or diarrhoea (erythema multiforme, Stevens-Johnson syndrome)

• Pain in the abdomen (stomach) which spreads to the back caused by inflammation of the pancreas
• Suicidal thoughts or attempting to kill yourself
• Nervousness, forgetfulness, confusion, fitting (seizures), abnormal thoughts
• blurred vision
• A feeling of spinning or tilting (vertigo)
• Yellow skin or eyes, itching, or pain in the abdomen (stomach) caused by inflammation of the liver
• Breast enlargement in males
• Angry behaviour, feeling of extreme happiness or contentment, seeing or hearing things that are not really there (hallucinations), mania (mental condition characterised by episodes of overactivity, elation or irritability), paranoia, catatonia (condition in which the patient is rendered motionless and speechless for a period)
• Whistling, ringing or other persistent noise in the ears
• Tremor (shaking)
• flushing.


Post a comment