Do you think that it is fairly safe to substitute Sustiva for both Norvir and Invirase in a drug combination that already includes Zerit and Epivir? I very badly want to minimize the nasty lipodystrophy side effects. However I am concerned that substituting only one new drug now for two PIs might not fully surpress the virus, especially in view of my past drug history. Even though I could go back to my successful two PI regimen, I may be using up my NNRTI option (never used before) prematurely. Here are the particulars: My viral load is currently

Answer:

Well, the key part to your question disappeared... but it is still an important issue.

There is tremendous interest in preventing/reversing side effects currently attributed to the PI's (like both Norvir/ritonavir & Saquinavir) - by using a nonnuke - like Sustiva instead. Whether this substitution will work to reverse the body shape changes is still under investigation - the early reports from those who did substitute are not describing rapid reversals. So whether it just takes longer, or whether the PI's are actually the culprit - is still unclear. More clear is the role the PI's play in increasing blood fats like cholesterol - and so for some that alone may be enough of a reason to try a substitution.

So - when can we substitute safely? The key is to look at the combination that will be created after the substitution to judge how well it would work - for example if it was used as the initial combo. So for example - if you are now on zerit and epivir and the two PI's - and are now considering being on zerit/epivir and sustiva - the question is how well would those three work for you even if you had never taken the PI's. And those three can work dramatically well - when all three meds are active. BUT we would worry a lot more about that triple if there was prior resistance to the zerit and/or the epivir - like if either was used in a combination that was not fully suppressive. If that was the case then we would not be so confident that this substitution could work as well. We also know that the combination of norvir and saquinavir can, just by themselves, be enough to suppress HIV in many - especially for those with a viral load below 100,000. The same would not be true for Sustiva alone - so these two PI's can do more of the "work" if the d4T and/or 3TC was less potent due to prior resistance.

Hopefully that provides some of the thinking about when a substitution is safer to consider - since I would agree that if all you have is that nonnuke class left - you do not want to waste it in the wrong combo - especially since there are newer drugs coming that might work quite well when combined with that nonnuke - sometimes waiting may be better than risking it...

good luck. CC