A reduced dose of atazanavir (Reyataz) boosted by ritonavir may be safe and effective, and a way of reducing the cost of antiretroviral therapy in resource-limited settings, according to a Thai study published in the October 1st edition of the Journal of Acquired Immune Deficiency Syndromes.
The small retrospective study involved patients who took a reduced 200mg daily dose of atazanavir boosted by 100 mg of ritonavir once a day. This was taken with other antiretroviral drugs. All the patients maintained an undetectable viral load, and CD4 cell count increased significantly. There were also modest falls in blood fats.
But it is notable that the average weight of the patients was low, and the researchers are calling for further studies to confirm their findings.
The standard daily dose of atazanavir is 300mg boosted by 100mg of ritonavir.
The drug has a number of attractive characteristics. Most notably, it only needs to be taken once daily. Treatment with the drug involves fewer pills than other protease inhibitors. Furthermore, it did not cause the lipid increases that can be caused by other drugs from this class.
However, cost of atazanavir restricts its availability in resource-limited countries. To lower the cost of the drug, researchers wanted to see if a reduced dose of 200mg atazanavir boosted by 100mg of ritonavir was safe and effective.
They reviewed the medical records of 14 patients taking antiretroviral therapy whose viral load was undetectable (below 50 copies/ml) at the time they switched to a 200mg dose of boosted atazanavir. All the patients were also taking two nucleoside reverse transcriptase inhibitors (NRTIs). The researchers looked at long-term changes in CD4 cell count, viral load, and lipids in these patients.
The patients had an average age of 47 years and most (57%) were women. Of note, body weight was low, being a median of 53.5 kg. The patients were taking a variety of antiretroviral regimens before their switch to reduced-dose atazanavir.
At the time of switching to the reduced dose of atazanavir, the median CD4 cell count was 300 cells/mm3.
Patients were followed for a median of 68 weeks. All maintained an undetectable viral load and median CD4 cell count increased to 420 cells/mm3, a statistically significant change (p
None of the patients stopped their treatment because of side-effects.
Information on trough blood levels of atazanavir were available for five patients, and all had levels above the minimum target of 150 ng/ml.
“In this cohort study, we demonstrated the long-term efficacy of low-dose atazanavir/ritonavir 200/100 once daily as part of an antiretroviral regimen”, write the investigators, adding that their results “provide some evidence that this regimen is adequate in HIV-positive patients in Thailand”.
The investigators conclude, “this combination markedly lowers the cost of treatment [and] is safe, well tolerated and has a low pill burden compared with other protease inhibitors and therefore should be considered as a boosted protease inhibitor regimen in resource-limited settings”.
They call for a full pharmacokinetic study and larger clinical trial to confirm their findings.
Chetchotiskd P et al. Low-dose, once-daily atazanavir/ritonavir (200/100): an effective treatment for HIV-infected patients in Thailand. J Acquir Immune Defic Syndr 49: 230-1, 2008.