HIV Treatment

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Drug Resistance

Last Reviewed: March 16, 2020

Key Points

  • Once a person gets HIV, the virus begins to multiply in the body. As HIV multiplies, it sometimes changes form (mutates). Some HIV mutations that develop while a person is taking HIV medicines can lead to drug-resistant HIV.
  • Once drug resistance develops, HIV medicines that previously controlled a person’s HIV are no longer effective. In other words, the HIV medicines can't prevent the drug-resistant HIV from multiplying. Drug resistance can cause HIV treatment to fail.
  • Drug-resistant HIV can be transmitted from person to person or develop after a person starts taking HIV medicines.
  • Drug-resistance testing identifies which, if any, HIV medicines won’t be effective against a person’s HIV. Drug-resistance testing results help determine which HIV medicines to include in an HIV regimen.
  • Taking HIV medicines every day and exactly as prescribed (called medication adherence) reduces the risk of drug resistance. 

What is HIV drug resistance?

Once a person gets HIV, the virus begins to multiply in the body. As HIV multiplies, it sometimes changes form (mutates). Some HIV mutations that develop while a person is taking HIV medicines can lead to drug-resistant HIV.

Once drug resistance develops, HIV medicines that previously controlled the person’s HIV are no longer effective. In other words, the HIV medicines can’t prevent the drug-resistant HIV from multiplying. Drug resistance can cause HIV treatment to fail.

Drug-resistant HIV can spread from person to person (called transmitted resistance). People with transmitted resistance have HIV that is resistant to one or more HIV medicines even before they start taking HIV medicines.

What is drug-resistance testing?

Drug-resistance testing identifies which, if any, HIV medicines won’t be effective against a person’s HIV. Drug-resistance testing is done using a sample of blood.

People with HIV should start taking HIV medicines as soon as possible after their HIV is diagnosed. But before a person starts taking HIV medicines, drug resistance testing is done. Drug resistance test results help determine which HIV medicines to include in a person’s first HIV regimen.

Once HIV treatment is started, a viral load test is used to monitor whether the HIV medicines are controlling a person’s HIV. If viral load testing indicates that a person’s HIV regimen isn’t effective, drug-resistance testing is repeated. The test results can identify whether drug resistance is the problem, and if so, can be used to select a new regimen.

How can a person taking HIV medicines reduce the risk of drug resistance?

Taking HIV medicines every day and exactly as prescribed (called medication adherence) reduces the risk of drug resistance. Skipping HIV medicines allows HIV to multiply, which increases the risk that the virus will mutate and produce drug-resistant HIV. 

Before starting HIV treatment, tell your health care provider about any issues that can make medication adherence difficult. For example, a busy schedule or lack of health insurance can make it hard to take HIV medicines consistently. Once you start treatment, use a 7-day pill box or other medication aid to stay on track. You can download the AIDSinfo Drug Database app to set daily medication reminders.

The following AIDSinfo resources offer more information on drug resistance and medication adherence:

This fact sheet is based on information from the following sources:

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