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resistance
Aug 12, 2006

i want to know througout your experience what the minimal time of expositiion on haart patient can occured an resistance

Response from Dr. Sherer

The time required to develop resistance to HIV drugs is not uniform; it varies by class of drug and by individual agent.

Resistance to the NNRTIs, such as nevirapine (Viramune) and efavirenz (Sustiva), and to lamivudine (Epivir) can occur very rapidly, within hours to days. In single drug trials of lamivudine, for example, a strong 1.5 log viral load drop after the first drug exposure was lost after an average of 7 days due to the rapid development of resistance. That is one reason why we use triple combination of drugs from at least two different classes of drugs.

Resistance to the above drugs only requires a single mutation, i.e. one amino acid substitution, to render the virus resistant to the drug.

In contrast, resistance to most nucleoside reverse transriptase inhibitors takes weeks to months. Resistance to these drugs requires several amino acid mutations, and hence a longer time to evolve.

Resistance to protease inhibitors is greatly reduced with higher drug levels, as are achieved with boosting with ritonavir, and can take months or years to evolve.

The simple answer to your question, then, is that resistance can occur in a short period of time, eg less than one month, with some regimens, e.g. those based on NNRTIs and/or containing epivir, IF there has been a lapse in regular drug concentrations, e.g. due to poor adherence, impaired drug absorption, drug interactions that lower blood levels, or other causes.

For these reasons, HIV clinicians advise their patients to try to be PERFECT with their drug adherence, i.e. to take every dose as described, and never to skip doses, halve the doses to make a drug supply last an extra week.

I urge you to talk to your doctor about this concern and this answer.


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