People with HIV who take Atripla (tenofovir/emtricitabine/efavirenz) take longer to reach virologic failure (if it occurs) and are less likely to develop drug resistance than those who take an equivalent combination therapy as separate pills. These findings are an important indication of the potential risks of prescribing Atripla’s individual components as a cost-savings measure as the respective antiretrovirals lose patents and cheaper generic versions of the drugs enter the market.

Publishing their findings in the journal AIDS, researchers culled a sample of 58 people who took Atripla and 128 who took equivalent regimens with multiple pills. The data on these individuals was drawn from eight prospective clinical cohorts in Europe and North America and four randomized controlled trials. The potential Atripla-equivalent regimens included Truvada (tenofovir/emtricitabine) plus Sustiva (efavirenz), Viread (tenofovir) plus Emtriva (emtricitabine) and Sustiva (efavirenz), or Viread (tenofovir) plus Epivir (lamivudine) and Sustiva (efavirenz). (Epivir is a similar drug to Emtriva.) For the most part the individuals in the analysis were treatment naive; those who were treatment experienced had never experienced virologic failure.

There was no significant difference in virologic failure rates among those who were in cohort studies. However, among those in the cohort studies who took Atripla, the time to virologic failure was 350 days on average, compared with just 211 days in the Atripla-equivalent regimens. This difference was highly statistically significant, meaning it is highly unlikely to have occurred by chance.

Sixty-eight percent of those in the overall sample who experienced virologic failure developed drug resistance. Fifty-three percent of those in the Atripla group developed one or more drug-resistance mutations, compared with 74 percent in the Atripla-equivalent group—a highly statistically significant difference. The severity of the drug resistance’s impact was spread similarly: Those in the Atripla group had a Genotypic Sensitivity Score of 52 percent, while those in the Atripla-equivalent group had a score of 72 percent.

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