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Being Alive

MEDICAL UPDATE: Latest on AZT vs. ddI


Being Alive 1993 Mar 5: 5

We have reported in the past on the results of the ACTG 116B and 117 studies. In these studies, all subjects had to have been on AZT therapy for at least 16 weeks prior to the start of the study. Three study groups were formed; one was on 750 mg of ddI a day, the second on 500 mg of ddI, and the third on 600 mg of AZT. What researchers found was that the group on 500 mg of ddI (400 mg in the new formulation) had a statistically significant lower incidence of new opportunistic infections than did the other two groups. For those already on AZT, it appeared that a low dose ddI might be a superior antiviral.

But what about those people who have never been on AZT or who have taken AZT less than 16 weeks? Would ddI still be superior in lowering the incidence of AIDS-defining OIs? ACTG 116A was designed to address these questions.

Again, three groups were formed: high dose ddI, low dose ddI, and AZT. All subjects had to have never taken AZT or been on AZT less than 16 weeks prior to the study. The results of 116A, presented at a recent International AIDS Society conference, were surprising. For those never on AZT prior to the study, 600 mg of AZT per day resulted in a statistically significant lowering of new OIs, over either the 500 or 750 mg dosage of ddI. For those on AZT between 8-16 weeks prior to the study, however, the 500 mg of ddI proved to be superior in forestalling new OIs.

These results tell us that AZT appears to be superior to ddI in those who never had AZT before. For those who have had AZT for as short a time as 8 to 16 weeks, however, low dose ddI appears to be superior. This has left many researchers scratching their heads.

The 116B/117 results seemed consistent with the AZT resistance problem. Long term AZT use can bring on resistant strains of the virus. For such a person, ddI would be superior. But less than 16 weeks of AZT use is too short a time to cause viral resistance. So why the 116A results? The consensus of the experts at the conference was: "we don't know!" Because of so many unanswered questions, these study results do not call for switching to ddI after eight weeks on AZT. We need to understand these results better before acting on them. As noted AIDS researcher Paul Volberding remarked, "I guess there's some real important information here, but I'm not sure I understand it. The message may be to get people tested and to get them on some therapy." 


Information in this article was accurate in March 5, 1993. The state of the art may have changed since the publication date. This material is designed to support, not replace, the relationship that exists between you and your doctor. Always discuss treatment options with a doctor who specializes in treating HIV.