For those of you who can get on Medpage Today (http://www.medpagetoday.com/MeetingCoverage/DDW/26404), there is an interesting interview by Dr. Muir from Duke about using these drugs. He explains very simply how they work and if patients don't respond to one, why they should not be given the other one. At this point they believe there are overlapping resistant variants. There needs to be a lot more studying done before they will know if prescribing the "other" drug will lead to not being able to try the 4 drug combos that are coming eventually.