Adherence means taking a medication regimen exactly as it is prescribed. So if a drug such as one of the single-tablet HIV regimens should be taken once a day, having good adherence would mean taking the tablet daily as faithfully as possible.
The main goal of HIV treatment is to fully suppress the virus so that your routine viral load tests consistently come back undetectable. This will help keep your CD4 levels, a sign of your immune system’s health, as high as possible. Being undetectable doesn’t mean there is no virus in your body or that it’s not replicating (making any copies of itself). It’s just that undetectable HIV is replicating to such a small extent that standard tests can’t detect it. (The great news, however, is that your risk of transmitting HIV to others is vanishingly small, and may even be zero, when you’ve had a fully suppressed virus for at least six months.)
Taking your meds as prescribed is a vital way to keep you undetectable so you can live a long and healthy life with HIV. Missing a dose or two here and there likely won’t hurt you—today’s crop of HIV meds tends to have good “dosing forgiveness,” as it’s called. But poor adherence to your pill-taking schedule can give the virus the chance to replicate and send your viral load into detectable territory.
This is important because a detectable viral load can open the door for the virus to develop resistance to your antiretrovirals. (It does this by mutating when it replicates.) Having a drug-resistant virus may mean that certain HIV meds don’t work well for you anymore. So you might have to switch your drug regimen and may find that your options for replacement meds are limited. (There are currently 29 approved individual ARVs; people typically take three or four HIV meds in combination. There are also six different once-a-day, single-tablet regimens.)
Adherence may become even easier in the future. A two-drug injectable HIV treatment, given once every four weeks, recently entered Phase III clinical trials. Such advanced studies are the last step before a drug company can apply to the U.S. Food and Drug Administration (FDA) for approval. ViiV Healthcare’s long-acting cabotegravir and Edurant (rilpivirine) could hit the market by 2019. For those who have trouble sticking to a daily pill regimen or just want a different option, this could greatly simplify HIV treatment.