Q and A


Can resistance develop after a year with good adherence?

If someone is talking ART and having an undectable viral load for a year, will there be any chance to develop drug resistance, even if he or she is having strict adherence.

I read an article that sometimes drug resistance occurs even under strict adherence.


Thanks – this is a good question.

For treatment to be undetectable (less than 50 copies/mL) for more than a year proves the all the drugs in a combination are active and working. If someone did have drug resistance before starting ART, viral load would have rebounded much earlier.

This means that so long as you are good taking meds drug resistance will not be a problem in the future.

Apart from low adherence, the few cases when new resistance is reported can sometimes be due to drug interaction. For example, if you start new medicines or supplements that interact with your HIV meds this might make them less effective. This is why your HIV doctor needs to know about any other meds you used.

Also, this answer is based on being “undetectable” using viral load tests that have a cut-off of 50 copies/mL (as in the UK). Drug resistance can still develop on ART when viral load is between 50 and 1000 copies/mL.

When viral load tests with higher cut-offs of 500 copies/mL or 1000 copies/mL are used drug resistance might still develop. These less sensitive tests are still used in some countries. However, resistance is still more likely to happen during the first year than at any time later.

Your doctor can tell you which resistance tests are used in your country. Continuing to take your meds carefully is the best way to avoid drug resistance in the future. This risk is also very rare after a year.


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