Why Does HIV Resistance Occur?

Question: Why Does HIV Resistance Occur?

Your doctor has probably mentioned HIV resistance at one time or another since your diagnosis. HIV resistance is a major concern of your physician, because if it does occur, your medication regimen will not work as well as it once did. In fact, certain types of HIV resistance can render an entire class of HIV drugs useless. So the questions are why does HIV resistance occur in the first place and can you do anything to prevent it from occurring?

Answer: To understand HIV resistance, we have to review a little information about HIV medications and how they work. The goal of HIV medications is to prevent HIV replication, to prevent the production of viral copies. The goal of any HIV regimen is to keep the HIV viral load undetectable, meaning the number of active viral copies is below the sensitivity of the viral load blood test. Medications do this by interfering with the replication of HIV. Here's how that is done:

• A combination of medicines are used to attack HIV at different stages in the viral life cycle. Working together, these medicines interfere with viral processes that occur during the replication process. Years ago, treatment was limited to one or two medications attacking one or two stages in the life cycle. Unfortunately, this method of treatment allowed the virus to find ways to "work around" the one or two medication regimen, allowing the virus to replicate and viral mutations to occur. With the advent of more medications, regimens of at least three drugs (and sometimes more) are now being prescribed. Using a combination of medicines in this matter makes it more difficult for the virus to "work around" the drugs.
• In order to achieve the maximum effect from your medication regimen, there must be therapeutic levels of each drug circulating in the bloodstream at all times. The circulating medications keep the virus at bay, interfering with the HIV life cycle and preventing viral replication. This, in turn, keeps active virus levels low, decreasing the chances of selecting for viruses with resistance-conferring mutations.

Viral Resistance occurs when the level of medication in your blood is not high enough to interfere with and slow HIV replication. As new viral copies are made, small genetic changes (mutations) occur that allow HIV to effectively replicate even in the presence of medication combinations. When HIV is able to replicate in the presence of medications, HIV resistance has occurred.

What Causes Medication Levels to Fall?

Medication levels in your blood fall below therapeutic levels when:

• you are late taking a dose of medication;
• you miss a dose entirely because you forget or you just decide not to take the dose for one reason or another;
• you take your medicines but not the way your doctor prescribed.

Simply put, if you do not adhere to your medicines as prescribed, blood levels will fall and viral replication will accelerate. As a result, some of the new copies exhibit small genetic changes or mutations make it possible for replication to occur even in the presence of medications, and what results from all this is medication resistance.

Important Note!
The best way to prevent resistance is to take your medicines as prescribed each and every day.

For more information about ways to prevent resistance:

• Adherence Strategies that Can Work for You
• 10 Tips that Help You Take Your Medicines Each and Every Time
• Medication Adherence Resources