What is Efavir (Efavirenz)?

Efavir is taken with other antiretroviral medications to treat patients infected with HIV-1. The main component of Efavir is efavirenz, and it is available in 200mg and 600mg tablets. The drug cannot stop the progression of HIV to AIDS on its own; it must be part of a regimen of anti-HIV medications. Adding only Efavir to a currently failing regimen is also insufficient.

Dosage & Administration

The recommend dose of Efavir for adults is 600mg once daily. Administering Efavir without food may help improve adverse intestinal effects. Pediatric patients who weigh greater than 40kg can take the recommended dose for adults, but smaller children should be dosed based on the following guidelines: Those weighing between 10kg and 15kg should be limited to 200mg of Efavir once a day; those between 15kg and 20kg can take up to 250mg once a day; those between 20kg and 25kg can take up to 300mg once a day; those between 25kg and 32.5kg can take up to 350mg once a day; and patients between 32.5kg and 40kg may take 400mg once a day. This medication is not safe for children who are younger than three years of age or weigh less than 10kg.

Contraindications

Any patient with a history of hypersensitivity to efavirenz should not take Efavir. Patients who take ergot alkaloids, midazolam, astemizole, cisapride or triazolam should avoid this drug.

Efavir Side Effects

Side effects associated with Efavir include:

• impaired concentration
• rash
• dizziness
• abnormal dreams
• insomnia

Severe side effect include:

• suicidal idealization or attempts
• manic reactions
• severe depression
• paranoid reactions
• aggressive behavior
• hallucinations
• somnolence

There may be other side effects that have yet to be recorded. Tell your doctor right away if you feel any changes in your health when beginning Efavir.

Precautions & Warnings

Nervous system system side effects typically begin within a couple of days after starting Efavir and cease in two-four weeks. Those with a previous history of psychiatric illness may be at a greater risk for psychiatric symptoms. Rashes often resolve on their own but can rarely become serious. Some patients who have had seizures in the past experienced convulsions while taking the drug. Patients with hepatitis or who are taking other treatments metabolized by the liver, such as concomitant anticonvulsants, must have their plasma levels and liver enzymes monitored while on Efavir. It is also recommend that patients taking this medicine have their triglycerides and cholesterol checked on a regular basis.

Interactions

Efavir may lower CYP3A4 substrate concentrations in plasma. Rifabutin, rifampin, phenobarbital and other drugs that interact with CYP3A4 activity can quicken Efavir's elimination from the body leading to reduced plasma concentrations. The drug can inhibit 2C9, 3A4 and 2C19 isoenzymes. Patients also taking products metabolized by these isoenzymes may require dosing adjustments.

Pregnancy & Lactation

Efavir may contaminate breast milk. Women with HIV should avoid breat feeding to prevent the risk of transmitting the virus to their infant.

Overdose

The effects of taking more Efavir than recommended are undocumented. Do not take more than the prescribed amount.

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