Efavirenz is an oral medication that is used for the treatment of infections with the human immunodeficiency virus (HIV). Efavirenz is in a class of drugs called reverse transcriptase inhibitors which also includes zalcitabine (Hivid), zidovudine (Retrovir), didanosine (Videx), and lamivudine (Epivir). It is in a subclass of reverse transcriptase inhibitors referred to as non-nucleoside reverse transcriptase inhibitors that includes nevirapine (Viramune), and delavirdine (Rescriptor). 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 continually producing, 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 new DNA. Efavirenz directly inhibits the activity of reverse transcriptase and blocks the production of DNA and new viruses. Efavirenz does not kill existing HIV virus and it is not a cure for HIV. Efavirenz was approved by the FDA in 1998.

Sustiva

GENERIC AVAILABLE: No

Yes

The most common side effects of efavirenz are:

• rash,
• dizziness,
• confusion,
• insomnia,
• headaches,
• diarrhea,
• nausea, and
• vomiting.

Other side effects include

• muscle pain (myalgia),
• abnormal heartbeats,
• liver failure,
• increased cholesterol
• increased triglyceride levels.
• drowsiness,
• abnormal dreams,
• hallucinations, and
• difficulty concentrating.

Serious psychiatric adverse effects such as depression, suicidal thoughts, manic reactions, and aggressive behavior have been reported in patients taking efavirenz. Immune reconstitution syndrome which is an inflammatory response to infection may occur in patients treated with combination antiretroviral therapy.

The recommended dose for adults is 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 should be administered on an empty stomach to improve absorption, preferably at bedtime.

Efavirenz has many drug interactions because many drugs affect its breakdown and elimination by the liver. Efavirenz also affects the breakdown of other drugs by the liver. The following are some examples of drugs that interact with efavirenz.

Triazolam (Halcion), midazolam (Versed), bepridil (Vascor), pimozide (Orap), and ergot derivatives (for example, ergotamine, dihydroergotamine) should not be combined with efavirenz because efavirenz increases blood levels of these drugs, potentially causing serious adverse effects. St. John's wort should not be combined with efavirenze because it reduces blood levels of efavirenz, leading to possible loss of effectiveness.

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 ritonavir (Norvir) while Ritonavir increases the concentration of efavirenz. Increased drug concentrations may result in more frequent or more serious side effects.

There are no adequate studies in pregnant women. Data from an antiretroviral pregnancy registry revealed birth defects in 17 of 604 live births in women who took efavirenz during the first trimester.

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

What preparations of efavirenz are available?

Capsules: 50 and 200 mg. Tablet: 600 mg.

How should I keep efavirenz stored?

Efavirenz should be stored at room temperature, 15 C to 30 C (59 F to 86 F).