Table 21. Guidelines for Changing an Antiretroviral Regimen for Suspected Drug Failure

  • Criteria for changing therapy include a suboptimal reduction in plasma viremia after initiation of therapy, re-appearance of viremia after suppression to undetectable, significant increases in plasma viremia from the nadir of suppression, and declining CD4+ T cell numbers. Please refer to the more extensive discussion of these on page 19.
  • When the decision to change therapy is based on viral load determination, it is preferable to confirm with a second viral load test.
  • Distinguish between the need to change a regimen due to drug intolerance or inability to comply with the regimen versus failure to achieve the goal of sustained viral suppression; single agents can be changed in the event of drug intolerance.
  • In general, do not change a single drug or add a single drug to a failing regimen; it is important to use at least two new drugs and preferably to use an entirely new regimen with at least three new drugs. If susceptibility testing indicates resistance to only one agent in a combination regimen, it may be possible to replace only that drug; however, this approach requires clinical validation.
  • Many patients have limited options for new regimens of desired potency; in some of these cases, it is rational to continue the prior regimen if partial viral suppression was achieved.
  • In some cases, regimens identified as suboptimal for initial therapy are rational due to limitations imposed by toxicity, intolerance or nonadherence. This especially applies in late stage disease. For patients with no rational options who have virologic failure with return of viral load to baseline (pretreatment levels) and declining CD4+ T cell count, there should be consideration for discontinuation of antiretroviral therapy.
  • Experience is limited with regimens using combinations of two protease inhibitors or combinations of protease inhibitors with NNRTIs; for patients with limited options due to drug intolerance or suspected resistance these regimens provide possible alternative treatment options. There is limited information about the value of restarting a drug that the patient has previously received. Susceptibility testing may be useful in this situation if clinical evidence suggestive of the emergence of resistance is observed. However, testing for phenotypic or genotypic resistance in peripheral blood virus may fail to detect minor resistant variants. Thus, the presence of resistance is more useful information in altering treatment strategies than the absence of detectable resistance.
  • Avoid changing from ritonavir to indinavir or vice versa for drug failure, since high level cross resistance is likely.
  • Avoid changing among NNRTIs for drug failure, since high level cross resistance is likely.
  • The decision to change therapy and the choice of a new regimen requires that the clinician have considerable expertise in the care of people living with HIV. Physicians who are less experienced in the care of persons with HIV infection are strongly encouraged to obtain assistance through consultation with or referral to a clinician with considerable expertise in the care of HIV-infected patients.

From: Guidelines for the Use of Antiretroviral Agents in HIV-Infected Adults and Adolescents

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