Pharmacokinetics profile of serum and cellular Sofosbuvir along with its concentration effect analysis in HCV patients receiving Sofosbuvir and Ribavirin.

Sofosbuvir along with ribavirin is being widely used for treatment of HCV in Pakistan but it may show delayed response and reoccurrence of disease in some cases. The aim of the study was to investigate pharmacokinetics and concentration effect analysis of sofosbuvir. HCV patients (n=100) received 400 mg sofosbuvir along with low dose or weight based ribavirin (400 mg). Nonlinear mixed effects modeling (NONMEM) and unpaired t-test were used for the association of concentrations and treatment outcomes. Average day 10 sofosbuvir metabolite BM 331007 concentration was higher in patients having haemoglobin nadir value <10 g/dl compared to the patients having heamoglobin nadir value >10 g/dl (5.34 versus 4.87 pmol/106 cells; p=0.03). The average concentration trends of GS331007 at day 10 was towards being higher in the patients achieved sustained virologic response (SVR) as compare to the patients relapsed (5.19 versus 4.86 pmol/106 cells; p=0.05). Sofosbuvir (GS331007) thresholds concentration (suggested at day 10 through receiver operating characteristic curve) was 5.4 pmol/10