Detailed Drug Information:

DRUG CLASS AND MECHANISM: Efavirenz is an oral medication that is used for the treatment of infections with the human immunodeficiency virus (HIV). It is similar to nevirapine (Viramune) and delavirdine (Rescriptor). Efavirenz is in a class of drugs called reverse transcriptase inhibitors which also includes zalcitabine (Hivid), zidovudine (Retrovir), didanosine (Videx), and lamivudine (Epivir). During infection with HIV, the HIV virus multiplies within the body's cells. The newly-formed viruses then are released from the cells and spread throughout the body where they infect other cells. In this manner, the infection continually spreads to new, uninfected cells that the body is continuallyproducing, and HIV infection is perpetuated. When producing new viruses, the HIV virus must manufacture new DNA for each virus. Reverse transcriptase is the enzyme that the virus uses to form this new DNA. Efavirenz directly inhibits the activity of reverse transcriptase and blocks the production of DNA and new viruses. Unlike zidovudine, efavirenz does not need to be converted to an active form. Efavirenz does not kill existing HIV virus and it is not a cure for HIV. Efavirenz was approved by the FDA in 1998.

PREPARATIONS: Capsules: 50, 100 and 200 mg. There also is a 600 mg tablet for once-daily treatment.

STORAGE: Store at room temperature, 15-30°C (59-86°F).

PRESCRIBED FOR: Efavirenz is used for the treatment of HIV infection.

DOSING: The recommended dose for adults 600 mg daily. Efavirenz must be administered in combination with other anti-HIV drugs because the HIV virus quickly becomes resistant to treatment when efavirenz is used alone.

Efavirenz may be administered without regard to meals, but a high fat meal increases theabsorption of efavirenz. Therefore, efavirenz should not be ingested with a high fat meal.

DRUG INTERACTIONS: Efavirenz increases the breakdown of saquinavir (Invirase) and indinavir (Crixivan). This leads to lower drug concentrations in the body and reduces the effect of saquinavir and indinavir.

Efavirenz increases the concentration of benzodiazepines (e.g., Valium, Ativan), ritonavir (Norvir) and ergotamine (Ergostat) in the blood. Ritonavir increases the concentration of efavirenz. Increased drug concentrations may result in more frequent or more serious side effects.

PREGNANCY: There are no adequate studies in pregnant women. Studies in pregnant monkeys show that efavirenz is harmful to the fetus.

NURSING MOTHERS: It is not known whether efavirenz is excreted in human breast milk. HIV infected mothers should not breast feed because of the risk of transmitting HIV to an infant that is not infected.

SIDE EFFECTS: The most common side effects are rash, dizziness, confusion, insomnia, headaches, diarrhea, nausea, and vomiting. Other side effects include muscle pain (myalgia), abnormal heartbeats and increased cholesterol levels.