Table of Contents

• What Is Drug Resistance?
• How Does HIV Drug Resistance Occur?
• How Do Mutations Occur Before Antiretroviral Therapy Is Started?
• How Do Mutations Occur During Antiretroviral Therapy?
• What Are Some of the Factors That Contribute to the Accumulation of Drug-Resistance Mutations During Therapy?
• Does a Rebound in Viral Load Mean That Drug Resistance Has Occurred?
• What Is Genotypic Testing?
• How Are Genotypic Test Results Reported?
• What Is Phenotypic Testing?
• What About Using Genotypic and Phenotypic Tests Together?
• Can Drug-Resistance Tests Be Used Before Someone Starts Antiretroviral Therapy for the First Time?
• Can Drug-Resistance Tests Be Used to Choose a New Drug Regimen After an Initial One Fails?
• Do Specialists Recommend Drug-Resistance Tests?
• How Can Drug Resistance Be Avoided?
• Resistance Tests in Use
• Glossary

What Is Drug Resistance?

There are many types of germs, or pathogens, that can enter the human body. These include viruses, fungi, bacteria, and protozoa. Once inside the body, the primary goal of a germ is to survive and reproduce.

Pharmaceutical drugs are designed to target these germs and kill them or prevent them from reproducing inside the body. If a germ continues to reproduce during treatment, it can alter itself -- or mutate -- to avoid the drugs. This is called drug resistance.

When drug resistance occurs, the drug -- or combination of drugs -- loses its ability to block the germ from reproducing. Over time, the treatment can stop working completely. It is important to prevent germs from reproducing during treatment to prevent drug resistance from occurring.