What is Efavirenz?

Melissa Barrett

Efavirenz is a medication that is used to treat the human immunodeficiency virus (HIV) by slowing the reproduction of the virus. It is very rarely used alone and is often prescribed with medicines such as tenofovir and emtricitabine as part of a highly active artiretroviral therepy (HAART). Efavirenz can also be combined with other antiretroviral drugs to help prevent HIV infection in healthcare workers who have been exposed to the virus through accidental needle-sticks.

Efavirenz can reduce the effectiveness of birth control pills.
Efavirenz can reduce the effectiveness of birth control pills.

Common side effects of efavirenz include upset stomach, headache, forgetfulness and insomnia. Mood changes, confusion and depression may also occur soon after beginning treatment. Usually these side effects diminish or disappear entirely over time. More serious side effects, such as blistering skin, psychosis and seizures, require immediate medical attention. This class of medicine can affect liver function, so visible signs of jaundice, such as yellowing of the whites of the eyes or skin, should be reported to a physician immediately.

Headache and forgetfulness are common side effects of efavirenz.
Headache and forgetfulness are common side effects of efavirenz.

Efavirenz can cause birth defects, especially when taken by a woman during the first trimester of her pregnancy. The medication can also reduce the effectiveness of hormonal birth control medicines. When using this medication, sexually active women should use condoms or a diaphragm to prevent pregnancy and should notify their doctor immediately if they think they might be pregnant. Women on efavirenz should not breastfeed.

Other prescription medicines, herbal supplements and over-the-counter medications can interact adversely with efavirenz. Some blood thinners and anti-depressants can interfere with the medicine’s effectiveness or increase its side effects. Over-the-counter medications might need to be restricted during treatment, because they can add extra stress to the liver. The use of herbal supplements, especially ones containing St. John’s wort, should be reduced or eliminated.

Normal dosing in adults is 600-800 milligrams a day, and it generally is taken once a day in pill or capsule form. Most of the psychological side effects occur within a few hours of taking the medication, so it is often suggested that it be taken at night. That way a patient can often sleep through the worst of the adverse effects.

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