W HEN SWITCHING REGIMENS : Never switch or add only one medication in a failing regimen When interpreting resistance report; remember that resistance to previously taken Arv's will not show up Consider cross-resistance between Arv's-AZT/D4T; NVP/EFV; amongst protease inhibitors Certain ARV's should not be used together: tenofovir and abacavir/ddI ; AZT and D4T; D4T and ddI Previous exposure to only ritonavir= will not show up on genotyping BUT will have lost all protease inhibitors At least 2, preferable 3 new active drugs Chance of success improve if a new drug class is used
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