Unboosted fosamprenavir is associated with low drug exposure in HIV-infected patients with mild-moderate liver impairment resulting from HCV-related cirrhosis.

OBJECTIVES: The aim of this study was to compare amprenavir pharmacokinetics in HIV/hepatitis C virus (HCV)-co-infected cirrhotic patients receiving non-boosted fosamprenavir 700 mg twice daily with HCV/HIV-co-infected non-cirrhotic subjects and HIV-mono-infected subjects receiving fosamprenavir/ritonavir 700/100 mg twice daily. Liver stiffness at baseline and alanine aminotransferase levels at baseline and during follow-up were measured in order to find a correlation between drug levels and liver fibrosis or hepatotoxicity.
METHODS: Amprenavir plasma concentration was determined by HPLC. Liver stiffness was measured by transient elastometry. Liver function tests were determined every 1-3 months during follow-up.
RESULTS: Nineteen HIV-infected patients were included. Eight had chronic HCV hepatitis (group NC), five had HCV-related liver cirrhosis (group C) and six were HIV-mono-infected (group M). In group C patients, amprenavir C(trough), AUC(0-12) and half-life were 86%/83%, 64%/55% and 58%/59% lower when compared with controls and co-infected subjects without cirrhosis, respectively; conversely, drug clearance in cirrhotics was 181%/124% higher. In 3/5 cirrhotic patients (60%) and in 2/14 non-cirrhotic patients (14%), C(trough) was below the minimum target concentration of 400 ng/mL; nonetheless, in all these patients, HIV viral load was undetectable. No correlation was found between amprenavir pharmacokinetics and liver stiffness or hepatotoxicity at follow-up.
CONCLUSIONS: On the basis of these data, it seems reasonable to boost fosamprenavir with ritonavir even in cirrhotic patients; amprenavir pharmacokinetics could not be predicted by liver stiffness and seem not to predict hepatotoxicity at follow-up.