antibioticsbooks

236 PART 5 Antiviral Drugs
Adverse Effects
Musculoskeletal: Raltegravir has been associated
with increases in creatine phosphokinase. Most
of these cases have been asymptomatic; clinically
evident myositis or rhabdomyolysis is rare.
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Important Facts
• Cobicistat isn’t an antiviral, but rather a “pharmacokinetic
enhancer”: much like ritonavir, it
is used to “boost” the concentrations of other
drugs. In this case, it enhances the blood levels
of elvitegravir. In fact, right now elvitegravir
is ONLY available in combination with cobicistat
(and tenofovir and emtricitabine). Thus,
concerns for drug interactions for the combination
elvitegravir product are similar to those
for ritonavir-boosted protease inhibitors. In
contrast, raltegravir has few documented drug
interactions, a considerable advantage over
many antiretrovirals.
• Like the NNRTIs, the INSTIs have a low
genetic barrier to resistance, such that they
would be less “forgiving” of imperfect adherence
than a PI-based regimen.
What They’re Good For
These drugs have been studied both as add-ons
for patients with drug-resistant HIV and as initial
therapy in treatment-naïve patients.
Don’t Forget!
Pretty much the only drug raltegravir has an
interaction with is the anti-TB drug rifampin.
Rifampin is a potent inducer of drug-metabolizing