The effect of low-dose ritonavir monotherapy on fasting serum lipid concentrations

Objectives Ritonavir (RTV) at doses of 400 mg twice a day (bid) or higher adversely affects serum lipids. However, the effect of RTV 100 mg bid on serum lipids is unknown. We conducted a study to evaluate the effect of RTV 100 mg bid on fasting serum lipid profiles in HIV-negative healthy volunteers. Methods Ritonavir 100 mg bid was administered for 14 days to 20 healthy HIV-seronegative adults with normal serum lipids. After a 7-day washout, lopinavir/ritonavir (LPV/RTV) 400/ 100 mg bid was administered for 14 days. Fasting serum lipid parameters were measured twice at baseline, after 14 days of RTV, and after 14 days of LPV/RTV, and comparisons were made at each time-point for levels of total cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, the total/HDL cholesterol ratio and triglycerides. Results After 14 days of RTV 100 mg bid, total cholesterol level increased by 10.2% (P < 0.001), LDL cholesterol level increased by 16.2% (P < 0.001), triglyceride levels increased by 26.5% (P < 0.001), HDL cholesterol level decreased by 5.4% (P < 0.01) and the total/HDL cholesterol ratio increased by 17.3% (P < 0.001). The addition of LPV 400 mg bid to RTV 100 mg bid resulted in no significant further changes in LDL cholesterol or triglyceride level or total/HDL cholesterol ratio, but there were significant increases in both total cholesterol (8.0% increase; P = 0.007) and HDL cholesterol levels (6.7% increase; P = 0.008). Conclusions Ritonavir dosed at 100 mg bid significantly increased the concentration of total cholesterol, LDL cholesterol, total/HDL cholesterol ratio and triglycerides and reduced HDL cholesterol concentration. The addition of LPV 400 mg bid to RTV 100 mg bid further increased both total and HDL cholesterol levels without affecting the total/HDL ratio.