Antiretroviral regimens are usually changed for one or more of the following reasons: an unacceptable level of drug toxicities and/or side-effects; problems with adherence; failure to control viral load; not effective drug combination; change in medical condition and/or acquisition of other illness.
Regimen change can include: selecting all new drugs; adding an agent from a class not currently included in the regimen, adding a boosting agent to increase trough drug levels, adding a drug to strengthen a drug combination, switching out one drug for another from the same class to lessen pill burden, toxicity, or side-effects.
Newly developed drugs, new drug classes, and treatment strategies have made HIV therapy easier for many patients. It may be possible to switch to drugs that are taken less often and/or have a lower pill burden, including fixed-dose formulations that combine two or more drugs in a single pill. Treatment simplification usually works best when people are on one of their first regimens and have minimal drug resistance.
Drug toxicity, whether related to a particular drug or to a whole drug class, is one of the most common reasons for changing a first antiretroviral regimen. Toxicity ranges in effect from manageable side-effects (headache) to adverse events that cause morbidity and mortality (hypersensitivity). Some side-effects lessen or resolve after continued exposure to a drug.
Many patients change regimens if they are experiencing side-effects they find difficult to tolerate, including metabolic complications such as lipodystrophy (body fat changes) or elevated blood fat levels. Side-effects can be temporal (injection-site reactions), reversible (through changing the offending drug in the regimen), or long-term (atherosclerosis).
HIV has probably not developed extensive drug resistance if viral load remains suppressed. In this case, switching is generally safe and the focus can be on finding equally effective drugs with fewer toxicities. If the change is being made to simplify a regimen or to reduce side-effects with a particular drug, it may be possible to change just the one problematic drug. With over 20 antiretroviral drugs now available, it is often possible to change to a new regimen that causes fewer side-effects and enables better adherence.—Modified from www.aidsmap.com