You answered a question of mine on 10/18 regarding use of Reyataz. Currently I am on Ziagen, Viread, Reyataz w/Norvir. I developed resistance to Sustiva in 2003 so I believe that family of drugs is no longer an option for me (that is the only drug I am resistant to at this time). In your response (on 10/18) you stated that you do not prescribe Ziagen and Viread together because of the possibility of overlapping resistance pattern. I'm not clear on what that actually means so could you please clarify that for me. I'd also really like to get your recommendations on what you would prescribe as an alternative approach. Thank you very much for your time and information.

The issue is that a single mutation (at codon 65) confers resistance to both tenofovir and abacavir, so that the combination is more prone to fail than others. A combination of zidovudine and tenofovir may well avoid this problem, although it cannot be taken once a day. This being said, if you are on the regimen you describe and are responding to it, there is no clear reason to change, as the tenofovir/abacavir combination can be an effective backbone, as long as the third drug is a protease inhibitor, offering a higher barrier to resistance than a non-nucleoside drug would.