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Lexiva (fosamprenavir)

Pronunciation(s): lex-EE-vah; foss-am-PREH-nah-veer

What is Lexiva?

  • Lexiva is an HIV medication. It is in a category of HIV medicines called protease inhibitors (PIs). Lexiva prevents cells infected by HIV from producing new virus. This reduces the amount of virus in your body.
  • Lexiva, manufactured by ViiV Healthcare, was approved by the U.S. Food and Drug Administration on October 20, 2003.
  • In some parts of the world, fosamprenavir is sold under the brand name Telzir.
  • Lexiva must be used in combination with other HIV drugs. Along with other medications, Lexiva is often combined with low doses of Norvir (ritonavir), another protease inhibitor used to boost the amount of Lexiva in the bloodstream (which makes Lexiva more effective against HIV, including drug-resistant HIV, and easier to take).
  • There is a patient assistance program (PAP) for people living with HIV who do not have private or public health insurance and are unable to afford Lexiva. To learn more about the PAP for Lexiva, call 877-784-4842 or refer to the program's website for more information. For those with private health insurance, a program has been established to help cover each Lexiva co-payment, up to $100 every month. To learn more about this co-pay program, check out mysupportcard.com.

What is already known about Lexiva?
  • The FDA has approved three different dosages for Lexiva, which can be taken with or without food:
    • two 700mg tablets twice daily,
    • two 700mg tablets in combination with one or two100mg capsules of Norvir once daily, or
    • one 700mg tablet in combination with one 100mg capsule of Norvir twice daily.
  • For HIV-positive people who have failed other protease inhibitors in the past, the FDA-recommended dose is one 700mg Lexiva tablet in combination with one 100mg capsule of Norvir twice daily. Once-daily dosing may be possible for HIV-positive people who have used other protease inhibitors in the past, but needed to stop because of side effects.
  • For children, a liquid version of Lexiva was approved by the FDA in June 2007. There are three dosing options for children, depending on their body weight and age: To learn about treatment options for children, click here.
  • Clinical trials have determined that Lexiva is safe and effective when combined with other drugs, most notably two nucleoside reverse transcriptase inhibitors (NRTIs). Clinical trials have also concluded that Lexiva, combined with Norvir, is an effective option for people who are beginning HIV treatment for the first time and those who have tried and failed other protease inhibitors in the past.
  • For HIV-positive adults beginning HIV drug therapy for the first time, once- or twice-daily Lexiva plus Norvir is listed as an "alternative" protease inhibitor option by the United States Department of Health and Human Services in its treatment guidelines. This means that it is safe and effective to use, after consideration is given to the "preferred" protease inhibitor options. To learn more about these recommendations and options, click here.
  • If your viral load becomes detectable while taking a drug regimen that contains Lexiva, your doctor can order a drug-resistance test to see which drugs your virus are becoming less sensitive to. If your doctor finds that your virus is becoming resistant to Lexiva, it might be possible to begin taking a low dose of Norvir—if you're not already on one—to boost the amount of Lexiva in the bloodstream. This may help overcome low-level resistance to Lexiva and help push viral load back down to undetectable levels.
  • Many of the currently available protease inhibitors are affected by cross-resistance. This means that, if you've tried and failed a drug regimen in the past that contained a protease inhibitor, your virus might be resistant to Lexiva. Similarly, if you take an HIV drug regimen that contains Lexiva and your virus becomes resistant to the drug, your virus might also be resistant to many of the other protease inhibitors available. This is why it is very important to use drug-resistance testing to determine which drugs your virus are no longer responding to if you experience a rebound in your viral load while taking an HIV drug regimen. Drug-resistance testing can also help you figure out which protease inhibitors your virus is still sensitive to.

What about drug interactions?
  • Lexiva is broken down (metabolized) by the liver, like many medications used to treat HIV and AIDS. This means that Lexiva can interact with other medications. Lexiva can lower or raise the levels of other medications in the body. Similarly, other medications can lower or raise the levels of Lexiva 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.
  • Based on what we know about the drug interactions with Lexiva, the following medications should not be taken while you are being treated with Lexiva:
    Acid reflux/heartburn medications: Propulsid (cisapride)
    Antimigraine medications: Methergine, Methylergometrine (methylergonovine); Ergostat, Cafergot, Ercaf, Wigraine (ergotamine); Ergotrate, Methergine (ergonovine); or D.H.E. 45, Migranal (dihydroergotamine)
    Antibiotics: Rifadin (rifampin)
    Cholesterol-lowering drugs (statins): Zocor (simvastatin) and Mevacor (lovastatin)
    Antipsychotics: Orap (pimozide)
    Sedatives: Versed (midazolam) and Halcion (triazolam)
    Enlarged prostate: Uroxatral (alfuzosin)
    Pulmonary Hypertension: sildenafil, used as Revatio
  • If Lexiva is combined with low-dose Norvir, the following medications should also be avoided:
    Antifungals: Vfend (voriconazole)
    Antihistamines: Hismanal (astemizole) or Seldane (terfenadine)
    Heart medications: Cordarone (amiodarone), Vascor (bepridil), Tambocor (flecainide), Rythmol (propafenone), or Quinaglute/Quinidex (quinidine)
    Enlarged prostate: Uroxatral (alfuzosin)
  • Anticonvulsants, such as Tegretol (carbamazepine) and Luminal (phenobarbital) can decrease the amount of Lexiva in the bloodstream. It might be necessary to increase your dose of Lexiva if you are taking any of these drugs. Taking Lexiva with Dilantin (phenytoin), however, lowers blood levels of Dilantin, so the Dilantin dosage may need to be increased.
  • Based on what we know about the drug interactions with Lexiva, it is likely that other HIV drugs can interact with Lexiva. HIV protease inhibitors can interact with Lexiva. Norvir (ritonavir), Kaletra (lopinavir/ritonavir), Reyataz (atazanavir), Crixivan (indinavir), and Viracept (nelfinavir) may all increase Lexiva levels in the bloodstream. An increased rate of side effects have been seen when people combine Lexiva with Kaletra, and the two should not be used together. Invirase (saquinavir) may decrease the amount of Lexiva in the bloodstream, and studies have not established a safe way to combine Invirase and Lexiva.
  • HIV non-nucleoside reverse transcriptase inhibitors (NNRTIs) can also interact with Lexiva. Sustiva (efavirenz) and Viramune (nevirapine) may decrease the amount of Lexiva in the bloodstream. Rescriptor (delavirdine), can increase levels of Lexiva in the bloodstream. No dosing recommendations have been made, although low-dose Norvir may be necessary if Viramune is combined with Lexiva. An additional 100mg (total 300mg) of Norvir may be needed if Lexiva is used once-daily with Sustiva. No additional Norvir is recommended if Lexiva is dosed twice-daily. Using Lexiva with either Rescriptor or Intelence is not recommended.
  • It's possible that Ziagen (abacavir), an NRTI, can increase Lexiva levels in the bloodstream. However, there is no need to change the dose of either drug.
  • Lexiva can interact with some medications used to treat TB, MAC, and other bacterial infections. Rifadin (rifampin) can decrease Lexiva levels (these drugs should not be used together). Lexiva can increase Mycobutin (rifabutin) levels and Mycobutin may decrease Lexiva levels (the Mycobutin dose will likely need be reduced). Biaxin (clarithromycin) increases Lexiva levels, although no dosing changes will likely be necessary.
  • Lexiva can interact with some medications used to treat thrush (candidiasis) and other fungal infections. Lexiva can increase Nizoral (ketoconazole) and Sporanox (itraconazole) levels in the bloodstream. Similarly, Nizoral can increase Lexiva levels in the bloodstream. Doses of greater than 200 mg per day of Nizoral or Sporanox are not recommended.
  • Lexiva may decrease the amount of oral contraceptives (taken by women to help avoid pregnancy) in the bloodstream. This means that there may be a higher risk of becoming pregnant if Lexiva and oral contraceptives are taken at the same time. Similarly, oral contraceptives may reduce Lexiva blood levels and could lead to HIV treatment failure. To reduce the risk of pregnancy, barrier protection (e.g., condoms) should be used instead.
  • Cholesterol-lowering drugs, also known as "statins," can interact with Lexiva. The two statins that are considered to be the safest in combination with Lexiva are Pravachol (pravastatin) and Lescol (fluvastatin). It may also be possible to take Lexiva with Lipitor (atorvastatin), Crestor (rosuvastatin) and Mevacor (lovastatin), although Lexiva 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.
  • There is a class of drugs, known as PDE-5 inhibitors that are used to treat both erectile dysfunction and pulmonary arterial hypertension. Their brand names differ, depending on their use. Lexiva/Norvir can significantly increase blood levels of these drugs.

    When used to treat erectile dysfunction, it is best to use a lower dose of Viagra (sildenafil), Levitra (vardenafil) and Cialis (tadalafil) in order to reduce the risk of side effects. When used to treat pulmonary arterial hypertension, the dose of tadalafil (Adcirca) must be reduced if combined with Lexiva/Norvir. Revatio (sildenafil) and Lexiva/Norvir should not be used together.

  • Tracleer (bosenstan) is another type of drug used to treat pulmonary arterial hypertension, called an endothelin receptor antagonist. Lexiva/Norvir can increase Tracleer blood levels, so the dose of Tracleer should be reduced.

  • Blood levels of the antidepressants Paxil (paroxetine) and Desyrel (trazadone) are affected by Lexiva. Lexiva increases blood levels of Desyrel, which can increase the risk of Desyrel side effects. The dose of Desyrel may need to be lowered when taken with Lexiva. Conversely, Lexiva decreases blood levels of Paxil. The dose of Paxil may need to be increased when taken with Lexiva.
  • Lexiva/Norvir can increase blood levels of cochicine, which is used to treat gout. Lower doses of colchicine are recommended, and the two drugs should not be used together in people with liver or kidney impairment.
  • Lexiva/Norvir can increase blood levels of Advair, Flovent, or Flonase (fluticasone), the inhalable medications that are used to treat allergies and asthma. In turn, these drugs may decrease blood levels of Lexiva/Norvir. Alternatives to these drugs should be considered, especially for long-term use. Lexiva/Norvir can increase blood levels of an asthma medication called Serevent (salmeterol), a drug that is used to open the air passages in the lungs during an asthma attack. This can result in heart rhythm problems. Use of the two drugs together is not recommended.
  • Herbal products can also interact with Lexiva. St. John's wort should not be used with Lexiva, since it can greatly reduce the amount of Lexiva in the bloodstream. HIV-positive people should also be cautious about using garlic supplements or milk thistle with Lexiva—test tube studies suggest that both herbal products can interact with the same liver enzyme system (cytochrome P450 3A4) responsible for metabolizing Lexiva. This may alter the amount of Lexiva 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 Lexiva is combined with Norvir (ritonavir). To learn more about these drug interactions, click here.

What about side effects?
  • Short-term side effects include rash, appetite loss, headaches, feeling crummy (malaise), diarrhea, nausea, and vomiting. While these are the same side effects caused by Agenerase, many are less common with Lexiva. Very often, these side effects improve within a few months/weeks of starting Lexiva.
  • Severe, life-threatening rashes have been documented with Lexiva. People with a moderate rash and other allergic symptoms, and people with severe rashes should stop taking Lexiva.
  • HIV drug regimens containing protease inhibitors, including Lexiva, 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. These side effects of HIV drug therapy are reviewed in our lessons on Lipodystrophy, Facial Lipoatrophy, and Risks To Your Heart (Hyperlipidemia).

Can pregnant women take Lexiva?

  • Lexiva 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 HIV treatment to help protect their babies from HIV (see our lesson called Family Planning, Pregnancy & HIV).
  • It is not known whether Lexiva 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.

Who should not take Lexiva?

  • Lexiva has not been studied in children younger than 2 years of age.

Where can I learn more about clinical trials of Lexiva?
  • If you would like to find out if you are eligible for any clinical trials that include Lexiva, visit ClinicalTrials.gov, a site run by the U.S. National Institutes of Health. The site has information about all HIV-related clinical studies in the United States. For more info, you can call their toll-free number at 1-800-HIV-0440 (1-800-448-0440) or email contactus@aidsinfo.nih.gov.

Last Revised: February 07, 2011

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