antibioticsbooks

246 PART 5 Antiviral Drugs
Think of protease enzymes as a pair of scissors
that cut out prefabricated shapes from a piece of
cardboard paper—take away the scissors (with
protease inhibitors) and the shapes are just a
piece of paper.
Spectrum
Serine protease inhibitors are only useful against
hepatitis C virus. They have only been studied for
genotype 1 HCV infection, though they have some
activity against HCV genotype 2.
Adverse Effects
Both boceprevir and telaprevir have hematologic
adverse effects that compound those of pegylated
interferon and ribavirin, with which they must
be co-administered. The most notable of these is
anemia, which may require dose adjustment of
ribavirin and ultimately the use of erythropoietin
stimulating agents. They are both also associated
with additional nausea and dysgeusia (alteration
of taste).
Telaprevir commonly causes rash and pruritis
that ranges widely in severity. Rash tends to
appear after about two to three weeks of therapy
and may be manageable with topical therapies or
may require drug discontinuation depending on its
severity.
Telaprevir also causes anorectal discomfort
in a significant percentage of patients, generally
manifesting as hemorrhoids, rectal burning, and/
or pruritis. Uric acid elevations also occur and may
precipitate attacks of gout.