i was taking videx entriva and reyataz, my cd4 was undetected but my tcell 86, my doctor change to truvada, norvir and reyataz, but i heard itsnt good to take reyataz if taking norvi. can u tell me about it, and why cd4 can be undetected and tcells as low? thanx nelson

Nelson, thank you for your post.

For purposes of replying, I'll assume that this is your first drug regimen. The combination of ddI (Videx), FTC (Emtriva) and atazanavir (Reyataz) is not one of the more commonly prescribed treatments in the US, though it has some fans in the European Union. I'm guessing that your doctor is concerned about the possibility that ddI might be contributing to a lower than expected CD4 cell rise, though determining this would require knowing what your counts were before you started and how long you've been on treatment. The fact that your viral load is undetectable suggests to me that it might be premature to conclude that your CD4 cell count won't increase-- sometimes it just takes a little longer to see (despite having a good viral response).

Now, with regards to a switch to Truvada + ritonavir + atazanavir-- tenofovir (one of the halves of Truvada) interacts with atazanavir, significantly lowering the levels of the protease inhibitor (and also lowering the levels of tenofovir). Because of this, if tenofovir is to be taken with atazanavir, it's not only a good idea, but mandatory that the two drugs be taken with ritonavir (Norvir), to boost the atazanavir levels.

While the combination of Truvada + ritonavir + atazanavir is prescribed with some frequency, I'm not one of the big proponents. There simply isn't sufficient clinical trials data to blindly support the use, particularly in the face of many clinical trials that well characterize other combinations. Indeed, for this reason, ritonavir-boosted atazanavir is not even recommended in the most recent treatment guidelines for treatment naive persons from the US Department of Health and Human Services. This is not to say that the combination won't work, nor that the drug interactions cannot be overcome, but that I'll tend to stick to studied combinations and switch to newer combos once the study data confirms the hypotheses. To this point, the Truvada/Norvir/Reyataz combination is the subject of a number of ongoing (but yet-to-be presented) clinical studies.

The primary reason for my reluctance is the previously mentioned drug interaction and the need to take the medications with food and need to avoid antacids(other factors that can dramatically lower atazanavir exposure). We've substituted other nucleoside combinations with atazanavir (such as Combivir or Epzicom (Kivexa)) to avoid the extra ritonavir; or when there is a strong desire to use the Truvada nucleoside backbone, we more frequently will use ritonavir-boosted fosamprenavir (Lexiva, Telzir) or Kaletra.

Hope this helps, thanks for reading. BY