REPEATED PHARMACOKINETICS OF TENOFOVIR DISOPROXIL FUMARATE (TDF) IN HIV-INFECTED ADULTS RECEIVING SAQUINAVIR (SQV) HARD GEL/RITONAVIR (RTV) 1000/100 MG BID

In the case of lopinavir/RTV, co- administration with TDF increases tenofovir levels. Conversely, TDF reduces levels of co-administered atazanavir. Given the quite different elimination mechanisms between tenofovir and the hepatically metabolized PIs, the mechanism of these interactions, while still unclear, is likely to operate at the drug absorption stage. The unpredictability of these interactions and the popularity of TDF as a once-daily antiretroviral make it important that the pharmacokinetics of TDF in combination with other antiretroviral agents be examined on a case-by-case basis. The potential for drug-drug interactions between TDF and SQV hard gel/RTV combinations and the time needed for both to reach steady state when co-administered have not previously been explored. To measure tenofovir plasma pharmacokinetics 2 days after TDF administration and at steady state (day 13) in HIV-infected adults receiving SQV/RTV 1000/100 mg bid. Day 1 21.0 21.5 1.2 5.5 2.9 (9.0-38.0) (13.0-80.0) (0.9-1.6) (3.9-7.0) (0.8-6.4)