Basic
Informations
Isentress is an integrase
inhibitor manufactured by Merck & Company. It was approved by the
U.S. Food and Drug Administration (FDA) in October 2007. Isentress
is approved both for treatment-experienced patients who have HIV
strains that are resistant to multiple antiretroviral (ARV) drugs
and for people with drug-sensitive HIV strains, such as those
starting antiretroviral therapy for the first time.
After HIV's genetic material is deposited inside a cell, its RNA
must be converted (reverse transcribed) into DNA. A viral enzyme
called integrase then helps to hide HIV's DNA inside the cell's DNA.
Once this happens, the cell can begin producing genetic material for
new viruses. Integrase inhibitors, such as Isentress, are designed
to block the activity of the integrase enzyme and to prevent HIV DNA
from meshing with healthy cell DNA.
Isentress holds promise for
HIV-positive patients who no longer respond to other HIV drugs.
Because Isentress targets HIV differently than all other available
antiretrovirals, chances are that many people living with the
virus—regardless of which drugs have failed them in the past—will
likely benefit from using Isentress. Two large large Phase III
clinical trials have determined that Isentress, when combined with
other drugs, is effective for patients whose virus has adapted to
other HIV drugs used in the past. However, Isentress worked best
when it was combined with at least two other drugs that the virus
was sensitive to. For this reason, it is best to use drug-resistance
testing to determine which drugs your virus is sensitive to; the
results will show which antiretrovirals are best to combine with
Isentress.
Isentress is also approved for people who have not yet taken ARV
therapy. Isentress, combined with Truvada (tenofovir and
emtricitabine), is listed as a "preferred" option for first-time
treatment takers by the United States Department of Health and Human
Services in its official HIV treatment guidelines.
Drugs
Interactions
Isentress is broken down
(metabolized) by the body differently than most medications used to
treat HIV and AIDS. This means that Isentress likely has fewer drug
interactions when combined with protease inhibitors, non-nucleoside
reverse transcriptase inhibitors, methadone, opioid pain relievers,
statins, antifungals, proton pump inhibitors, oral contraceptives,
and erectile dysfunction drugs.
At the time of Isentress' approval in October 2007, there were no
known "contraindications," meaning that there are no known
medications that must be avoided while taking Isentress.
Isentress can interact with Rifadin (rifampin), a medication used to
treat TB, MAC, and other bacterial infections. Rifadin (rifampin)
can decrease Isentress levels in the bloodstream. While Isentress
dosing adjustments haven't been recommended, caution is recommended
if both drugs are used together.
Isentress can interact with a few HIV medications. Aptivus
(tipranavir), combined with Norvir (ritonavir), can decrease levels
of Isentress in the bloodstream. However, in a clinical trial
involving patients who took both drugs, treatment efficacy was not
compromised. Reyataz (atazanavir), combined with Norvir, can
increase Isentress levels in the bloodstream. In clinical trials,
this was not associated with an increased risk of Isentress side
effects. Based on these findings, Isentress dose adjustments are not
recommended if it is combined with either Aptivus/Norvir or
Reyataz/Norvir.
Isentress might interact with drugs that are called "UGT inducers."
These include, among other drugs, some anticonvulsants and some
atypical antipsychotics.
Interactions between Isentress and other medications may be
discovered. Tell your doctors and pharmacists about all medicines
you take. This includes those you buy over-the-counter and herbal or
natural remedies. Bring all your medicines when you see a doctor, or
make a list of their names, how much you take, and how often you
take them. Your doctor can then tell you if you need to change the
dosages of any of your medications.
Side
Effects
The side effects most commonly
reported among study volunteers who received Isentress were
diarrhea, nausea, and headache.
Blood tests showed abnormally elevated levels of a muscle
enzyme—creatine kinase—in some patients receiving Isentress.
According to the FDA, Isentress should be used with caution by
patients who are at an increased risk of muscle problems like
myopathy and rhabdomyolysis, which includes patients using other
medications known to cause these conditions.
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