When Should I Change My Treatments, and Which Drugs Should I Switch To? en español
What causes HIV to stop responding to therapy?
There are a number of possible reasons why anti-HIV therapy can stop working. These include:
Weak drug combinations (low potency). Some people living with HIV who have high viral loads before starting therapy—for example, over a million copies—might not see their viral load decrease to undetectable levels using just three drugs. Some researchers suggest that four or more drugs should be used to control very high viral loads. Be sure to talk with our doctor about the anti-HIV drugs you are taking to make sure you are on a potent (strong) combination of drugs.
Poor absorption. Absorption refers to the amount of drug that is absorbed into the bloodstream after being swallowed. If someone vomits a lot as a result of taking an anti-HIV drug or combination of drugs, this might affect the amount of drug that remains in the stomach and absorbed by the body. Not following dietary requirements carefully can also affect the amount of drug that is absorbed by the body. Some drugs must either be taken on an empty stomach or a full stomach. Make sure you understand how you are supposed to take your anti-HIV drugs with respect to food and liquids. And be sure to tell your doctor about any nausea, vomiting, or diarrhea you are experiencing.
Drug-drug interactions. Many drugs used to treat HIV—including all the protease inhibitors (PIs) and non-nucleoside reverse transcriptase inhibitors (NNRTIs)—are broken down in the body (metabolized) by an important liver enzyme known as P450. This enzyme is also responsible for metabolizing other common medications, including painkillers, antifungal drugs, birth-control pills, and antibiotics. Because of this, P450 can either increase or decrease the amount of anti-HIV drugs in the blood. Make sure you tell your doctor about any and all medications you are taking—either by prescription or over-the-counter—before starting anti-HIV therapy, and from then on.
We have a cool feature on this site that allows you to take the preventive step of determining whether the drugs you are taking interact with each other, or interact with a certain food, and cause a bad reaction in your body. Just click on Check My Meds for your personalized drug/drug & drug/food interactions report.
Poor adherence. Adherence refers to how well you follow your doctor's instructions regarding the medications you take. If you do not take your anti-HIV drugs exactly as prescribed—such as the correct number of times each day, every day—this can affect the amount of drug in your blood and, in turn, allow the virus to flourish. If you are missing doses of your anti-HIV drugs or do not understand how you are supposed to take them, be sure to tell your doctor immediately.
Drug resistance. Drug resistance—loosely defined as a series of changes, or mutations, in HIV's genetic structure that can render the virus less sensitive to anti-HIV drugs—is one of the most common and serious reasons for treatment failure. Some of the factors that can contribute to the development of drug resistance include the factors listed above, so it's important to understand what resistance is, how it can be avoided, and what to do if it occurs.
For a more complete understanding of adherence and resistance, click on the following lesson links:
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