Efavirenz is a Non-Nucleoside Reverse Transcriptase Inhibitor (NNRTI) drug used for the treatment of HIV-1 in combination with other antiretroviral drugs. Efavirenz binds to HIV-1 reverse transcriptase, disabling its function in viral replication.
Dosing & Administration
Efavirenz is indicated for the treatment of HIV-1 infection, and for HIV post-exposure prophylaxis in an occupational setting (off-label), as part of a three-drug combination regimen. It can be used in adults, children, and infants 3 months and older weighing at least 3.5 Kg. Despite approval for use, it is not recommended for children under three years old due to concerns about underdosing. Efavirenz comes in a hard capsule that cannot be scored, crushed or chewed, and in a capsule that can be opened and sprinkled. Efavirenz should be taken on an empty stomach. Dosing and administration instructions are given in the product monograph.
Efavirenz does not require dosage adjustments in patients with mild liver dysfunction, but the drug should not be used in moderate or severe liver impairment. Dosage adjustments are probably not necessary in renal-impaired patients.
Efavirenz is contraindicated in patients with hypersensitivity to the drug, or those with severe liver dysfunction, or in patients with a personal or family history of certain heart conditions. Efavirenz is also contraindicated for concurrent use with certain medications. Details are provided in the product monograph.
Efavirenz is associated with CNS effects often described as feeling high. Patients should be advised to take precautions with driving and other activities requiring attentiveness. Serious psychiatric effects have also been reported. A complete list of potential adverse effects is provided in the product monograph.
Efavirenz may prolong the QTc and should be used with caution in patients with cardiac disease or who take other medications that cause QTc prolongation.
Efavirenz should not be used in patients with moderate or severe liver dysfunction due to reports of serious hepatotoxicity, especially in patients with underlying liver disease.
All patients who test positive for HIV infection should be screened for comorbid Hepatitis B virus (HBV) and Hepatitis C virus (HCV) infection. Co-infected patients should be started on an antiretroviral regimen targeting co-infected viruses, regardless of CD4 counts or viral loads. Current HIV treatment guidelines outline drug regimens and prescribing considerations.
Efavirenz is associated with a large number of drug-drug and herbal interactions and contraindications. These are listed in the product monograph.
Pregnancy & Lactation
Efavirenz may be teratogenic and should be avoided in the first trimester of pregnancy. Women taking efavirenz should use two forms of contraception during treatment and continuing for 12 weeks after. Efavirenz is excreted in breast milk. The CDC recommends that all HIV positive women, treated or untreated, avoid breastfeeding to prevent vertical transmission of the virus.
Efavirenz overdose should be treated with standard supportive care, as no specific antidote is known. Efavirenz is not significantly dialyzable.
Alternative Brand Names
Efavirenz is also available under the brand name Sustiva, and as a component of the combination medication Atripla.
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