Isentress (raltegravir)

October 2007     View PDF     En español
Reprinted from www.aidsmeds.com, US

What is Isentress?
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 for treatment-experienced patients who have HIV strains that are resistant to multiple antiretroviral drugs. It is not yet approved 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 must be used in combination with other anti-HIV drugs.

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What is already known about Isentress?
The Isentress dose is one 400mg tablet taken by mouth twice a day. It can be taken with or without food.

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 not yet approved for people with HIV that have no, or limited, resistance to other available antiretroviral drugs. This includes HIV-positive people beginning treatment for the first time. However, preliminary data from a study evaluating the drug in patients new to HIV treatment suggest that Isentress is comparable to standard-of-care Sustiva (efavirenz), at least for 24 weeks of treatment. The FDA has not yet reviewed these data.

Isentress is not approved for use in HIV-positive children.

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What do we know from clinical trials of Isentress?
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.

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.

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What is known about 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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Who should not take Isentress?
Isentress is classified by the FDA as a pregnancy category C drug. Pregnancy category C means that animal studies have shown an adverse effect on the fetus and there are no adequate and well-controlled studies in humans, but potential benefits may warrant use of the drug in pregnant women despite potential risks. HIV-positive women who become pregnant should discuss the benefits and possible side effects of anti-HIV treatment to help protect their babies from HIV.

It is not known whether Isentress passes into breast milk and what effect it may have on a nursing baby. To prevent transmission of the virus to uninfected babies, it is recommended that HIV-positive mothers not breast-feed.

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Where can I learn more about clinical trials of Isentress?
If you would like to find out if you are eligible for any clinical trials that include Isentress, there is an interactive web site run by ACRIA, the AIDS Community Research Initiative of America.

Another useful service for finding clinical trials is AIDSinfo.nih.gov, a site run by the U.S. National Institutes of Health. NIH has “health information specialists” you can talk to at their toll-free number at 800.HIV.0440 (800.448.0440).

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