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zidovudine, Retrovir

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GENERIC NAME: zidovudine (AZT)

BRAND NAME: Retrovir

DRUG CLASS AND MECHANISM: Zidovudine is an oral and injectable medication that is used for the treatment of infections with the human immunodeficiency virus (HIV). It is in a class of drugs called reverse transcriptase inhibitors which also includes zalcitabine (Hivid), stavudine (Zerit), 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 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 make this new DNA. Zidovudine inhibits the activity of reverse transcriptase and blocks the production of DNA and new viruses. Specifically, zidovudine is converted within the body to its active form (zidovudine triphosphate). This active form is similar to the compound thymidine triphosphate, a chemical that is required by the HIV virus to make new DNA. The reverse transcriptase uses zidovudine triphosphate instead of thymidine triphosphate for making DNA, and it is the zidovudine triphosphate that interferes with the reverse transcriptase. Zidovudine does not kill existing HIV virus, and it is not a cure for HIV. Retrovir was approved by the FDA in 1987.

GENERIC AVAILABLE: Yes

PRESCRIPTION: Yes

PREPARATIONS: Capsules: 100 mg; syrup 50 mg/5 ml; injections 10mg/ml

STORAGE: Store at room temperature, 15-30 C (59-86 F). Keep capsules and syrup away from light.

PRESCRIBED FOR: Zidovudine is used for the treatment of HIV and the prevention of HIV transmission from an infected mother to her fetus.

DOSING: For the treatment of HIV infection the recommended oral dose for adults is 100 mg every 4 hours. The intravenous dose is 1 to 2 mg/kg every 4 hours.

For children 3 months to 12 years old, the oral starting dose is 180 mg/m2 every 6 hours not to exceed 200 mg every 6 hours.

Infants should be given 2 mg/kg orally every 6 hours within 12 hours of birth and for 6 weeks or 1.5 mg/kg intravenously every 6 hours.

To prevent HIV transmission from mother to fetus, the dose is 100 mg five times daily or 200 mg three times daily. Treatment should be initiated between the 14th and 34th weeks of pregnancy and continued until the time of labor. During labor and delivery, 2mg/kg should be administered intravenously over 1 hr followed by 1 mg/kg/hr until the umbilical cord is clamped.

DRUG INTERACTIONS: Fluconazole (Diflucan), probenecid and trimethoprim (Trimpex) reduce the elimination of zidovudine and therefore increase the blood concentration of zidovudine. This can lead to increased side effects from zidovudine.

PREGNANCY: Zidovudine is used for preventing transmission of the HIV virus from mother to fetus..

NURSING MOTHERS: Although it is not known whether zidovudine is excreted in breast milk, HIV infected mothers should not breast feed because of the potential risk of transmitting HIV to an infant that is not infected.

SIDE EFFECTS: The most severe side effects are a decrease in blood cells, muscle pain (myopathy) enlarged liver (hepatomegaly) and metabolic disturbance (lactic acidosis). Other side effects are chills, rash, confusion, dizziness, headache, diarrhea, nausea, and weight loss.

Reference: FDA Prescribing Information

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