ABSTRACT
Two polyethylene glycol (PEG)-modified interferons are approved for the treatment
of chronic hepatitis C. The pharmocokinetic properties of the branched 40 kDa pegylated
interferon alfa-2a differ from the linear 12 kDa pegylated interferon alfa-2b. The
absorption half-life of standard interferon alfa is 2.3 hours, while absorption half-lives
for peginterferon alfa-2a and alfa-2b are 50 hours and 4.6 hours, respectively. The
volume of distribution for peginterferon alfa-2a is considerably restricted, while
the volume of distribution for peginterferon alfa-2b is only approximately 30% lower
than that for conventional interferon. Because of its large size, the 40 kD peginterferon
alfa-2a has a more than 100-fold reduction in renal clearance compared with conventional
interferon alfa. Clearance of peginterferon alfa-2b is about one-tenth that of unmodified
interferon alfa. Although data are limited, both drugs appear to show differences
in the initial viral decay pattern in patients with chronic hepatitis C. However,
it remains unknown whether these differences in the initial viral decline predict
differences in the primary clinical endpoint, sustained virological response.
KEYWORDS
Peginterferon alfa-2a - peginterferon alfa-2b - pharmacokinetics - viral kinetics
