Efavirenz is contraindicated in patients with clinically significant hypersensitivity to any of its components. Efavirenz must not be administered concurrently with astemizole, cisapride, midazolam, triazolam or ergot alkaloids.
Warnings and Precautions:
- General: Efavirenz must not be used as a single agent to treat HIV or added on as a sole agent to a failing regimen.
- Psychiatric Symptoms: Serious psychiatric adverse experiences such as severe depression, suicidal ideation/attempts, aggressive behaviour, paranoid reactions and manic reactions have been reported in patients treated with Efavirenz. Patients with a prior history of psychiatric disorders appear to be at greater risk for these psychiatric adverse experiences.
- Rash: Patients should be informed that rash is another common side effect seen with Efavirenz. However, these rashes usually go away without any change in treatment. In a small number of patients, rash may be serious. Patients should be advised that they should contact their physician promptly if they develop a rash.
- Nervous System Symptoms: These include dizziness, insomnia, impaired concentration, somnolence, abnormal dreams and hallucinations. Nervous system symptoms usually begin during the first one or two days of therapy and generally resolve after the first 2-4 weeks. Dosing at bedtime seems to improve the tolerability of these symptoms.
- Convulsions: Convulsions have been observed infrequently in patients receiving Efavirenz, generally in the presence of known medical history of seizures. Patients who are receiving concomitant anticonvulsant medications primarily metabolized by the liver, such as phenytoin, carbamazepine and Phenobarbital, may require periodic monitoring of plasma levels. Caution must be taken in any patient with a history of seizures.
- Liver Enzymes: In patients with known or suspected history of hepatitis B or C infection and in patients treated with other medications associated with liver toxicity, monitoring of liver enzymes is recommended.
- Cholesterol: Monitoring of cholesterol and triglycerides should be considered in patients treated with Pregnancy:Category D.
- Nursing mother: Animal data suggest that Efavirenz may be passed into breast milk. It is recommended that HIV-infected mothers do not breast-feed their infants to avoid the risk of postnatal transmission of HIV infection.
Efavirenz is an inducer of CYP3A4 in vivo. Other compounds that are substrates of CYP3A4 may have decreased plasma concentrations when coadministered with Efavirenz. In vitro studies have demonstrated that Efavirenz inhibits 2C9, 2C19 and 3A4 isoenzymes in the range of observed Efavirenz concentrations. Coadministration of Efavirenz with drugs primarily metabolized by these isoenzymes may result in altered plasma concentrations of the coadministered drug. Therefore, appropriate dose adjustments may be necessary for these drugs. Drugs which induce CYP3A4 activity (e.g. Phenobarbital, rifampin, rifabutin) would be expected to increase the clearance of Efavirenz resulting in lowered plasma concentrations.
The most significant adverse events are nervous system symptoms, psychiatric symptoms and rash.
Dosage And Administration:
Adults: 600 mg orally, once daily.
Paediatric use: The following table describes the recommended dose of efavirenz for paediatric patients 3 years of age or older and weighing between 10 and 40 kg. The recommended dose of efavirenz for paediatric patients weighing greater than 40 kg is 600 mg once daily.
It is recommended that Efavirenz be taken on an empty stomach, preferably at bed time. Bed time dosing improves the tolerability of nervous system side-effects.
Paediatric dose to be administered once daily
|Body weight (kg)||Efcure dose (mg) |
|10 to < 15|| 200 |
|15 to < 20|| 250 |
|20 to < 25|| 300 |
|25 to < 32.5|| 350 |
|32.5 to < 40|| 400 |
|> 40|| 600 |