efavirenz, Sustiva

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GENERIC NAME: efavirenz

BRAND NAME: Sustiva

DRUG CLASS AND MECHANISM: 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.

GENERIC AVAILABLE: No

PRESCRIPTION: Yes

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

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

PRESCRIBED FOR: Efavirenz is prescribed for the treatment of HIV infection in combination with other anti-HIV drugs.

DOSING: 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.

DRUG INTERACTIONS: 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.

PREGNANCY: 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.

Medically Reviewed by a Doctor on 1/23/2013



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