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Substitute AZT for D4T in treatment experienced?
Mar 21, 2002

My doctor told me today that more recent studies now suggest that AZT really has very much the same resistance profile as D4T. Is this true?

The reason I ask is that I have been on D4T, DDI and Sustiva for the past two years (with no detectable viral load all of this time). I am concerned about the increasing lipidostrophy side effects of the D4T and DDI combination. My doctor suggested that substituting AZT for the D4T might help. However I was on AZT and then sequentially on AZT and DDI for a long time (in the late 1980s and early 1990s before resistance tests were available). I am probably somewhat mildly resistant to AZT, DDI and D4T (mistakenly taken with too low a dose of Viracept) because my CD4 began to drop on these previous combos. However I never had less than 34 CD4 or, to my knowledge, >3,000 VL.

Given this past history, I am also concerned that Sustiva is now doing most of the work and the risk of eventually developing resistance to the NNRTIs with either AZT (which might be less toxic) or D4T in the combo could be high in my case. This leads me to also ask you if substitution or addition of Ziagen or Viread is a possible other option to consider here to avoid D4T or the PIs? Or should I jsut stay with what I'm taking for now and hope and pray that the Sustiva will continue working for another year or two!

Thanks for all of your sage advice on this web page!

Response from Dr. Little

Well - you have raised a lot of good questions and I will try to answer then in order:

1. d4T and AZT do select for some of the same resistance mutations. They are not completely overlapping, but there are several common mutations that could be selected on either drug.

2. Based upon an undetectable viral load for 2 years on ddI/d4T/sustiva and your concern about lipodystrophy - if you are going to switch d4T out and another drug in, I would probably not pick AZT - mostly based upon your prior treatment experience with this drug. You do have several other options - if in fact you have not tried 3TC, abacavir, tenofovir. I would be more in favor of one of these choices if you have not had prior experience.

Hope this helps.

resistence testing
could a 3 week break from meds cause resistance

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