The currently approved antiretroviral drugs affect the replication cycle of HIV at different steps. In principle, five different viral replication steps are targeted by the current antiretroviral medications. Combining these medications in two or three drug regimen has been proven to be effective for long-term suppression of HIV in real life. Combining these drugs in one pill is a convenient solution, but some combinations may consist of two to three pills daily.
The first combination therapy should rapidly reduce the viral load below the limit of detection and suppress it continuously at low level to avoid the development of resistance and to guarantee long-term efficacy usually over many years. If there are efficacy problems or persisting side effects antiretroviral therapy should be switched.
If and how long an antiretroviral combination therapy works is dependent on the choice of a suitable combination and adherence to the dosing schedule. Taking your drugs according to your dosing schedule will most likely lead to a good and sustained efficacy of antiretroviral treatment.
In order to find the best treatment for you depending on dosing schedule, resistance profile of the virus and potential adverse events associated with the therapy, you should take your time to make an informed choice together with your physician.
Antiretroviral drugs can also lose their efficacy due to reasons other than non-adherence. Examples are
Your treating physician will monitor the antiviral efficacy by regular controls to detect any treatment failure as soon as possible.
In HIV infected patients about 10 billion new viruses are produced every day. By chance during this replication process altered viruses, so-called mutants, emerge. These have different features from the original virus, the so-called wild-type virus.
Some of these viral mutants accidentally develop resistance in the presence of antiretroviral therapy. They have a survival advantage in comparison to the wild-type virus, as they are no longer susceptible to the drugs. The resistant viruses grow despite the presence of antiretroviral therapy. Resistance development of the virus is not possible in the absence of viral replication. For this reason, fully suppressive antiretroviral therapy is the best way to prevent resistance.
The development of resistance is mostly promoted by:
The faster the viral load decreases below the limit of detection after the beginning of treatment the less likely it is that resistance will develop. After the development of resistance the decision about the next antiretroviral combination should be based on a resistance test of your HIV. This is performed in a laboratory after a blood sample is taken from you to culture and examine your virus. Unfortunately some resistance mutations confer cross-resistance to other antiretroviral therapies, which may narrow the treatment options considerably.