HIV Rebound and Resistance

In HIV treatment programs across the country, specialists are trying to outsmart the virus. Since the advent of protease inhibitors and other classes of HIV drugs, doctors have had the formidable task of finding the right combinations of medicines that keep the virus at bay. But with every successful regimen, there are failures. In fact studies now show that while drug "cocktails" suppress HIV in 60 to 90 percent of cases, 30 to 60 percent of those patients end up being considered treatment failures because of rebounding levels of the HIV virus later in there therapy course. The common thought was that over time the virus becomes resistant to medications allowing the virus to replicate. Two studies published in the January 2000 issue of JAMA, looked at treatment failure mechanisms, and adherence and drug potency. Data from these studies indicate that rebounding levels of HIV are not always a result of resistance. While researches are are certain resistance plays a major role in drug regimen failures, they also know that other factors contribute. While studies show the development of resistant strains of HIV in those patients who have had viral rebound, others factors were found to play a role, namely poor adherence to drug regimens and poor drug potency at the cellular level.

Adherence
Adherence has always been known to be a problem when taking HIV medications. Unpleasant side effects along with large pill burdens and stigmas attached to taking medications has made adherence difficult, even in the most motivated patient. Millions of dollars are spent each year trying to find ways to help patients be more successful in adhering to drug regimens. Unfortunately the cure all plan has not been found, and adherence continues to be a major problem in the care of HIV infected persons. The reality that adherence plays a major role in therapy failure necessitates a new push to help patients better adhere to their medicine regimens.

What's being done?
Programs are across the country are working harder than ever trying to improve adherence. Peer "buddy" programs using patients to remind or assist each other with taking medicines have been successful by encouraging patient responsibility in their own care. Drug companies are providing funding for educational programs, workshops, medication alarms, watches and other adherence tools. Research and development of new once a day and twice a day therapies continues making drugs more tolerable and easier to take by decreasing side effects, dosage frequency, and the number of pills that need to be taken with each dose. Experts believe a combination of all these techniques, specific to each patient's needs is the answer to adherence problems.

Drug Potency
Drug potency is becoming more important in the fight against resistance. A French study in 1998 looked at how well patients took their medicines and measured drug levels in the blood. While mutations attributed to resistance were noted, the researchers found that drug potency played a larger role in treatment failure and HIV rebound. This finding was confirmed with a similar study in the United States where it was determined that drug levels in the blood were a more important factor in fighting resistance.

What's being done?
Research has found that certain HIV drugs work better and are more potent when combined with one another. The protease inhibitor Norvir, once a backbone drug in many regimens, is now used in much lower doses to boost the effect and potency of other protease inhibitors. Invirase, another protease inhibitor is being studied to do the same thing. Improving potency is key in the durability and efficacy of an HIV regimen.

So the fight continues. When it seems a battle is won, one doesn't have to look far to find a battle being lost. But continued research and development is providing us with the weapons to win this fight.