There are multiple reasons which may lead to changing of antiretroviral therapy, including:
Intolerable side effects,
First trimester of pregnancy when the patient so elects.
There are no studies and no reliable estimate of the number of days, weeks, or months that constitute a clinically important interruption of one or more components of a therapeutic regimen that would increase the likelihood of drug resistance. If there is a need to discontinue any antiretroviral medication for an extended time, clinicians and patients should be advised of the theoretical advantage of stopping all antiretroviral agents simultaneously, rather than continuing one or two agents, to minimize the emergence of resistant viral strains.
Antiretroviral therapy should be stopped and or changed when there is evidence of:
Toxicity or intolerance to one or all drugs
Failure as evidenced by the patient becoming symptomatic and progressive decline of CD4 count and/or rise of viral load despite good adherence to antiretroviral treatment.
When changing treatment the following should be observed:
Never change a single drug in the combination if the cause of changing is treatment failure, but rather change at least two of the drugs.
If changing due to toxicity, change only the drug suspected to be causing the problem.
Never change to a single drug therapy
In selecting drugs choose drugs that have not been used before, drugs that do not have cross-resistance, and have no overlapping toxicities or drug-drug interactions.