In the case of HIV, if the virus is resistant to drugs this means that the drug is ineffective in combating viral replication and will need to be replaced.
If you adhere to your treatment regime then the amount of drug needed to control the HIV replication process will remain stable. This will therefore result in less viral replication. This is very important in reducing the likelihood of drug-resistant virus developing. HIV has the ability to replicate at an amazing rate, each time it replicates its genetic make up is slightly altered and mutations occur. These mutations are known as drug-resistant virus because they have the ability to replicate in the presence of drugs which were previously effective. This will result in a higher level of HIV in your bloodstream, a loss of CD4 cells and impaired immune function.
By adhering to your regime and ensuring the right amount of anti-HIV medication is constantly in your body, fewer mutations or drug-resistant virus are able to develop. This means your treatment will be effective for longer, your immune system will incur less damage and you will remain healthier for longer.