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AIDS InfoNet www.aidsinfonet.org Fact Sheet Number 448 FOSAMPRENAVIR (Telzir, Lexiva) WHAT IS FOSAMPRENAVIR? take ARV medications according to Fosamprenavir is a sulfa drug. If you are Fosamprenavir is a drug used for instructions, on schedule, and not to allergic to sulfa drugs, be sure to tell your antiretroviral therapy (ART). It is also skip or reduce doses. doctor. called Lexiva. In some countries, it is called HOW DOES IT REACT WITH Telzir. It is manufactured by ViiV OTHER DRUGS? Healthcare. Fosamprenavir is a pro-drug. HOW IS IT TAKEN? Fosamprenavir is broken down by the liver The drug you swallow is not active against Fosamprenavir is available as a tablet. The and can interact with other drugs that also HIV. It breaks down in the body to produce normal adult dose is 1400 milligrams (mg) use the liver. Combining these drugs the active form, which is the drug two times a day. The tablets are 700 mg, can change the amount of each drug in amprenavir (see Fact Sheet 445). so you will take 2 tablets at a time. your bloodstream and cause an under- Fosamprenavir can also be taken in various or overdose. New interactions are Fosamprenavir is a protease inhibitor. combinations with ritonavir to boost blood constantly being identified. Make sure These drugs prevent the protease enzyme levels. The exact dosing depends on that your doctor knows about ALL drugs from working. HIV protease acts like a whether you have already used any and supplements you are taking. chemical scissors. It cuts the raw material antiviral treatment, or any other protease for HIV into specific pieces needed to build inhibitor medication. Be sure that your Drugs to watch out for include other ARVs, a new virus. Protease inhibitors “gum up” health care provider knows your medication drugs to treat tuberculosis (see fact sheet these scissors. history. 518), erectile dysfunction (such as Viagra), and heart rhythm (antiarrhythmics), and A liquid form of fosamprenavir is also migraine headaches. Interactions are also WHO SHOULD TAKE IT? available. possible with several antihistamines, Fosamprenavir was approved in 2003 as sedatives, drugs to lower cholesterol and an antiretroviral (ARV) drug for people with The dose for children should be calculated anti-fungal drugs. HIV infection. A liquid version is approved based on their body weight. for approved for children at least 4 weeks  If fosamprenavir is taken with ritonavir old. If you have liver problems or damage, talk and efavirenz, the daily dosage of ritonavir to your doctor. You may need an adjusted may need to be increased. While antiretroviral therapy (ART) is dose of fosamprenavir.  Some birth control pills may not work recommended for all people living with if you are taking fosamprenavir. Talk to HIV, independent of your symptoms or Fosamprenavir is available as 700 mg your doctor about how to prevent an CD4 count, you and your doctor should tablets. It can be taken with or without unwanted pregnancy. consider your CD4 (T-cell) count, your viral food. It should be stored at room  Fosamprenavir causes major load, any symptoms you are having, and temperature. If you take fosamprenavir increases in blood levels of some your attitude about taking HIV medications. with ritonavir, be sure to keep the ritonavir antidepressants like Elavil and Tofranil. Fact Sheet 404 has more information about in your refrigerator or for up to 30 days at These drugs are sometimes used to treat guidelines for the use of ARV medications. room temperature (below 77 degrees F, or peripheral neuropathy (see fact sheet 555.) 25 degrees C). Unlike the original version However, Fosamprenavir decreases blood If you take fosamprenavir with other ARV of amprenavir, fosamprenavir does not levels of Paxil (paroxetine), an drugs, you can reduce your viral load to contain Vitamin E. antidepressant. A dose increase of Paxil extremely low levels, and increase your may be needed. Discuss use of CD4 counts. This should mean staying antidepressants with your doctor. healthier longer. WHAT ARE THE SIDE EFFECTS?  Fosamprenavir levels do not appear to The most common side effects are nausea, be affected by use of antacids. diarrhea, vomiting, rash, and headache.  Taking fosamprenavir with methadone WHAT ABOUT DRUG Some patients also felt numbness around can lower blood levels of both drugs. the mouth, and abdominal pain. Less than RESISTANCE? Check with your doctor if you use 1% of people get serious skin reactions, methadone. Watch for signs of excessive Many new copies of HIV are mutations. including Stevens-Johnson syndrome. The They are slightly different from the original sedation with buprenorphine. diarrhea in most cases can be controlled  The herb St. John's Wort (See Fact virus. Some mutations can keep with over-the-counter medications. multiplying even when you are taking an Sheet 729) lowers the blood levels of some ARV drug. When this happens, the drug protease inhibitors. Do not take it while Fosamprenavir can increase cholesterol taking fosamprenavir. will stop working. This is called “developing and triglycerides (a blood fat,) and the rate  Fosamprenavir increases blood levels resistance” to the drug. See Fact Sheet of heart attacks (see fact sheet 652.). See of several “statin” drugs used to lower 126 for more information on resistance. Fact Sheet 123 for more information on cholesterol levels. Some statins should not blood fats. Blood fats and cardiovascular be used. The dose of others should be Sometimes, if your virus develops risk should be measured before using reduced. resistance to one drug, it will also have fosamprenavir and regularly while it is resistance to other ARV drugs. This is used. called “cross-resistance”. Fosamprenavir Reviewed Jun 1, 2016 might not be cross-resistant with other protease inhibitors. Resistance can develop quickly. It is very important to A Project of the International Association of Providers of AIDS Care and the New Mexico AIDS Education and Training Center. Partially funded by the National Library of Medicine. Fact Sheets can be downloaded from the Internet at http://www.aidsinfonet.org