TreatmentUpdate82 - Vol. 9, No. 8 - pp. 1-2; October 1997
Sean Hosein

When AZT was first approved by the FDA (Food and Drug Administration), it was supposed to be taken every 4 hours. In a recent clinical trial called ACTG 320 (see next article), it was given 3 times daily. Now researchers in the US have completed a one-year study comparing the effects of AZT twice daily versus every 4 hours. They found no difference between the two groups when looking at the number of PHAs developing AIDS or dying. As well, they found no differences in changes in the levels of CD4+ cell counts or the amount of HIV in the blood. If a larger study confirms these results, then taking AZT twice daily may become a more common practice, perhaps even increasing compliance in people with complicated drug regimens.

Study details

Doctors recruited 320 HIV-infected subjects for this study, half of whom were randomly assigned to receive regimen A: AZT 100 mg/4 hours or regimen B: AZT 300 mg/12 hours. Nearly 90% of subjects were male, half were gay/bisexual men, 27% drug users and 15% had used AZT before entering the study. On average the CD4+ cell count was about 100 cells.

Results

Roughly 60% of people completed the study. Ten people died; 5 in each group. One death was due to a drug overdose and the rest were the result of complications due to AIDS. Eighteen percent of subjects on regimen A developed life-threatening infections while in group B the figure was 20%. This difference was not statistically significant. As well, there were no statistically significant differences in changes to CD4+ cell counts or levels of HIV (as measured by p24 antigen). The symptoms and severity of AZT toxicity were similar in both groups.

Other smaller studies have shown twice-daily doses of AZT to be beneficial. This is the first study to compare the safety and effectiveness of AZT 600 mg/day at different dose schedules. Straight from the capsule, AZT does not have anti-HIV activity. The drug must first be absorbed by cells and then activated inside the cell. Once activated, AZT remains inside a cell for at least 6 hours. By taking the drug less often, some researchers hope that AZT will do less damage to cells. Hopefully other studies will confirm the results seen in this study. Less frequent dosing may make pill taking less problematic and perhaps increase compliance.

REFERENCES:

1. Sheep DH, Ramirez-Ronda C, Dall L, et al. A comparative trial of Zidovudine administered every four versus every 12 hours for the treatment of advanced HIV disease. Journal of Acquired Immunodeficiency Syndromes and Human Retrovirology 1997;15:283-288.

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