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 bodys 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.

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 the14th 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.

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.

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.

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

Store at room temperature 15-30°C 59-86°F. Keep capsules and syrup away from light.