Enhancement of pharmacokinetic parameters of amprenavir when combined with low dose ritonavir (APV 600 mg/RTV 100 mg bid) and preliminary efficacy results

Low doses of ritonavir (rtv) are being used to enhance the pharmacokinetic (PK) properties of protease inhibitors (PIs) while reducing pill burden. Steady state APV C sub(min) is significantly increased with co-administration of rtv. Data from healthy volunteers has shown APV/rtv 600 mg/100 mg bid to be an optimal dosing combination. PK parameters were measured in 12 treatment-naive HIV infected adults 2 weeks after changing therapy from APV 1200 mg bid to APV 600 mg rtv 100 mg bid. NRTI therapy was unchanged (abacavir 300 mg/lamivudine 150 mg bid). PK samples were obtained over a 12 h dosing interval. In conclusion, the addition of low dose rtv (100 mg bid) to an APV containing regimen allows reduction of the total daily dose of APV (from 16 to 8 capsules daily) with improved pharmacokinetic parameters and maintained virologic suppression.