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AGENERASE

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Basic Informations

Agenerase is an anti-HIV medication. It is in a category of HIV medications called protease inhibitors (PIs). Agenerase prevents T-cells that have been infected with HIV from producing new HIV.

Agenerase is manufactured by GlaxoSmithKline Pharmaceuticals and was originally developed by Vertex Pharmaceuticals. The U.S. Food and Drug Administration (FDA) approved it for the treatment of HIV infection in 1999.

The manufacturer of Agenerase has also developed Lexiva (fosamprenavir), a "prodrug" of Agenerase. This means that fosamprenavir must be broken down inside the body before it can become active. Doing so increases the amount of drug in the blood, while at the same time decreasing the number of pills that must be swallowed every day. Lexiva was approved by the FDA in October 2003 and is now the preferred form of amprenavir.

Agenerase is no longer available in the United States. Because Lexiva is now the preferred form of amprenavir, GlaxoSmithKline began phasing out the sale and distribution of the 150mg Agenerase capsules beginning in late 2004. In October 2007, GSK ended the U.S. sale and distribution of the 50mg capsules and the liquid version of Agenerase, on account of the June 2007 approval of a liquid version of Lexiva. Liquid Agenerase will remain available in countries where liquid Lexiva is not yet available.

Drugs Interactions

Agenerase is broken down (metabolized) by the liver, like many medications used to treat HIV and AIDS. This means that Agenerase can interact with other medications. Agenerase can lower or raise the levels of other medications in the body. Similarly, other medications can lower or raise the levels of Agenerase in the body. While many interactions are not a problem, some can cause your medications to be less effective or increase the risk of side effects.

Tell your doctors and pharmacists about all medicines you take. This includes those you buy over-the-counter and herbal or natural remedies, such as St. John’s Wort. 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.

The following medications should not be taken while you are being treated with Agenerase:

  • Acid reflux/heartburn medications: Propulsid (cisapride)

  • Antibiotics: Priftin (rifapentine) and Rifadin (rifampin)

  • Antimigraine medications: Ergostat, Cafergot, Ercaf, Wigraine (ergotamine) or D.H.E. 45 (dihydroergotamine)

  • Antihistamines: Hismanal (astemizole) or Seldane (terfenadine)

  • Calcium channel blockers: Vascor (bepridil)

  • Cholesterol-lowering drugs (statins): Zocor (simvastatin) and Mevacor (lovastatin)

  • Antipsychotics: Orap (pimozide)

  • Sedatives: Versed (midazolam) and Halcion (triazolam)

Anticonvulsants, such as Tegretol ( carbamazepine), Luminal (phenobarbital), and Dilantin (phenytoin), may decrease the amount of Agenerase in the bloodstream. It might be necessary to increase your dose of Agenerase if you are taking any of these drugs.

Anti-HIV protease inhibitors can interact with Agenerase. Norvir (ritonavir), Kaletra (lopinavir/ritonavir), Reyataz (atazanavir), Crixivan (indinavir), and Viracept (nelfinavir) can all increase Agenerase levels in the bloodstream. If Agenerase is combined with either Norvir or Kaletra, the Agenerase dose should be reduced. Invirase (saquinavir) can decrease the amount of Agenerase in the bloodstream. At the same time, if Agenerase is combined with Kaletra, the Kaletra dose may need to be increased (Agenerase may decrease the amount of lopinavir in the bloodstream). If Agenerase is combined with Invirase, low-dose Norvir may be necessary to maintain Agenerase levels in the bloodstream.

Anti-HIV non-nucleoside reverse transcriptase inhibitors (NNRTIs) can also interact with Agenerase. Sustiva (efavirenz) and Viramune (nevirapine) can decrease the amount of Agenerase in the bloodstream (adding Norvir will be necessary to maintain Agenerase levels). A third NNRTI, Rescriptor (delavirdine), can increase levels of Agenerase in the bloodstream (Agenerase can significantly decrease Rescriptor levels in the bloodstream if they are used together). The combination of Rescriptor and Agenerase is not recommended.

Ziagen (abacavir), an NRTI, can increase Agenerase levels in the bloodstream. However, there is no need to change the dose of either drug.

Agenerase can interact with some medications used to treat TB, MAC, and other bacterial infections. Rifadin (rifampin) can decrease Agenerase levels (these drugs should not be used together). Agenerase can increase Mycobutin (rifabutin) levels and Mycobutin may decrease Agenerase levels (the Mycobutin dose will need be reduced). Biaxin (clarithromycin) increases Agenerase levels, although no dosing changes are necessary.

Agenerase can interact with some medications used to treat thrush (candidiasis) and other fungal infections. Agenerase can increase Nizoral (ketoconazole) levels in the bloodstream. Similarly, Nizoral can increase Agenerase levels in the bloodstream. However, no dosing changes are necessary.

It is not known what effect Agenerase has on oral contraceptives/birth-control pills. To reduce the risk of pregnancy, barrier protection (e.g., condoms) should be used.

Cholesterol-lowering drugs, also known as "statins," can interact with Agenerase. The two statins that are considered to be the safest in combination with Agenerase are Pravachol (pravastatin) and Lescol (fluvastatin). It is also possible to take Agenerase with Lipitor (atorvastatin), Zocor (simvastatin) and Mevacor (lovastatin), although Agenerase can increase levels of these three drugs in the bloodstream. If Lipitor, Zocor, or Mevacor are prescribed, it's best to begin treatment with the lowest possible dose of the drug and then increase the dose if necessary. Little is known about the newest statin, Crestor (rosuvastatin), although it is not expected to have any serious drug interactions with Agenerase or the other protease inhibitors.

Viagra (sildenafil), Levitra (vardenafil) and Cialis (tadalafil) levels in the bloodstream may increase when combined with Agenerase. In turn, it is best to use a lower dose of these drugs in order to reduce the risk of side effects.

Agenerase contains high amount of vitamin E. To avoid unnecessary side effects of vitamin E, HIV-positive individuals taking this drug should avoid taking vitamin E supplements.

Herbal products can also interact with Agenerase. St. John's wort should not be used with Agenerase, since it can greatly reduce the amount of Agenerase in the bloodstream. HIV-positive people should also be cautious about using garlic supplements or milk thistle with Agenerase—test tube studies suggest that both herbal products can interact with the same liver enzyme system (cytochrome P450 3A4) responsible for metabolizing Agenerase. This may alter the amount of Agenerase in the bloodstream. These and other herbal products should be used with caution, until further studies are conducted.

A number of other negative drug interactions are possible if Agenerase is combined with Norvir (ritonavir).

Side Effects

Short-term side effects include rash, appetite loss, headaches, feeling crummy (malaise), diarrhea, nausea, and vomiting. Another possible side effect is numbness/tingling around the mouth (perioral paresthesias). Very often, these side effects improve within a few months/weeks of starting Agenerase.

Anti-HIV drug regimens containing protease inhibitors, including Agenerase, can cause increased fat levels (cholesterol and triglycerides) in the blood, abnormal body-shape changes (lipodystrophy; including increased fat around the abdomen, breasts, and back of the neck, as well as decreased fat in the face, arms, and legs), and diabetes.