antibioticsbooks

240 PART 5 Antiviral Drugs
from healthy subjects who received the drug in
early clinical trials. The effect seems to be rare
in patients treated with maraviroc.
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Important Facts
• Enfuvirtide is administered as a subcutaneous
injection associated with substantial injection
site reactions; thus, it is generally reserved
for patients with the most difficult-to-treat,
multidrug-resistant strains of virus.
• Because maraviroc only blocks one of two
coreceptors for HIV, it will not be effective for
virus strains that primarily utilize the CXCR4
coreceptor for viral entry. Hence, before a
patient is started on maraviroc, a tropism test
must be performed to see whether the patient’s
virus “prefers” CCR5 (in which case maraviroc
may be useful) or CXCR4 (thus ruling out
maraviroc use).
• Maraviroc is a substrate of P450 drugmetabolizing
enzymes and, thus, there are
different dosage recommendations depending
on which other potentially interacting drugs
the patient is taking.
What They’re Good For
These drugs are mainly for use in treatmentexperienced
patients.
Don’t Forget!
Before initiating maraviroc, make sure you know
it’s “Trofile”—that’s the name of the test used
to determine the profile of its tropism (CCR5 vs.
CXCR4).