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Response from Dr. Young

Thanks Dav for your post.
The regimen of tenfovir (Viread), 3TC (Viread) and ritonavir (Norvir) boosted atazanavir (Reyataz) is used here in the US quite commonly. I certainly agree that you should be receiving a boosted PI regimen, given that you have acquired NNRTI resistant virus.
Therapeutic drug monitoring, like you've had, isn't done frequently here, but is commonplace in Western Europe-- your levels do suggest to me that your atazanavir levels are suprisingly and perhaps dangerously low.
This could occur for a variety of reasons, first is whether you're taking your medications with food or not- atazanavir is very poorly absorbed on an empty stomach; the use of antacids, like the proton pump inhibitor, omeprazole is similarly associated with very poor absorption of atazanvir. Because of these factors, be sure that you take your medications with food and avoid antacids.
Tenofovir also lowers atazanavir levels (boosted or not) by about 25%, another potential contributing factor.
Lastly, your levels might simply be due to rapid metabolism of the drug.
No matter what, your viral load results are reassuring, but if I were your doctor, I'd be concerned enough to consider a switch. You've already got some significant resistance; I'd really want to avoid placing you at risk for having further resistance.
Most likely a move to either ritonavir-boosted lopinavir (Kaletra) or fosamprenavir (Lexiva, Telzir) would make the most sense. Both have no significant food requirements or interaction with antacids or tenofovir.
I hope this helps, BY
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