Pharmacokinetics of tenofovir disoproxil fumarate and ritonavir-boosted saquinavir mesylate administered alone or in combination at steady state.

A phase I study was conducted to formally evaluate the steady-state pharmacokinetics (PK) of tenofovir disoproxil fumarate (TDF) and ritonavir (RTV)-boosted saquinavir mesylate (SQV) when coadministered in healthy volunteers. Forty subjects received multiple doses of TDF (300 mg, once daily) and SQV/RTV (1,000 mg/100 mg, twice daily) alone and together under steady-state conditions in an open-label, fixed sequence design. Blood samples for tenofovir (TFV) and SQV/RTV PK were drawn over respective 24- and 12-h dosing intervals, and drug concentrations were measured by liquid chromatography-tandem mass spectrometry.