Plasma and intracellular concentrations of lopinavir and ritonavir in HIV-1 infected children.

Values between brackets are expressed as medians (25th percentile – 75th percentile). P values were determined using a Mann Whitney U test. All patients administered Kaletra (lopinavir + ritonavir) +2 NRTIs once daily. RBCLB+ = PBMCs treated with red blood cell lysis buffer. RBCLB-  =  PBMCs not treated with red blood cell lysis buffer. The RBCLB+ group consisted of 16 HIV-1 infected children. For one child, concentrations were determined during two separate visits at the outpatient clinic. RBCLB- group consisted of 8 HIV-1 infected children. Three children were included in both the RBCLB+ group and RBCLB- group as for these patients samples were processed with and without RBCLB. Plasma concentrations were determined by HPLC-UV and intracellular concentrations by MALDI-triple quadrupole MS. For one patient in the RBCLB- group, intracellular concentration of lopinavir was below the LLOQ while the intracellular concentration of ritonavir was above the LLOQ. Hours after intake  =  time difference in hours between medication intake and drawing of the blood sample. PBMC processing time  =  time difference between drawing of the blood sample and aliquoting of the PBMC.