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| Summary Amprenavir (Agenerase) is a type of anti-HIV medicine called a protease inhibitor. Some side effects associated with the use of amprenavir include nausea, diarrhea, rash and headache. In Canada and the European Union, the use of amprenavir is restricted to those people with HIV/AIDS (PHAs) who have previously used protease inhibitors. Amprenavir is available in capsules and as a liquid. What is amprenavir? Amprenavir, sold under the brand name Agenerase, is a type of anti-HIV medication called a protease inhibitor (PI). How does amprenavir work? To explain how amprenavir works, we need to first tell you some information about HIV. When HIV infects a cell, it takes control of that cell. HIV then forces the cell to make many more copies of the virus. In order to make these copies, the cell uses proteins called enzymes. When the activity of these enzymes is reduced or blocked, production of HIV slows or stops. Amprenavir belongs to a group of drugs called protease inhibitors. These drugs affect an enzyme called protease which is used by HIV-infected cells to make new viruses. Since amprenavir inhibits or reduces the activity of this protease enzyme (hence the name "protease inhibitor"), this drug causes HIV-infected cells to produce fewer viruses. The protease inhibitor amprenavir is usually used in combination with at least two other anti-HIV drugs from different classes, such as nucleoside analogues (nukes) and non-nukes. Combinations such as this are called highly active antiretroviral therapy, or HAART. For many PHAs, the use of HAART has increased their CD4+ cell counts and decreased the amount of HIV in their blood (viral load). These beneficial effects help to reduce a PHA's risk of developing a life-threatening infection. Side effects Here is a list of common side effects that may be experienced by some amprenavir users:
Other possible side effects may include the following:
Lipodystrophy syndrome
The precise cause(s) of the
lipodystrophy syndrome is not clear. Moreover, there may be several
syndromes occurring at the same time in the same PHA. The role of
protease inhibitors and other drugs in lipodystrophy is also not clear.
Researchers are studying the lipodystrophy syndrome in an effort to find
out what causes it and how it can be managed.
Treatment-experienced PHAs can have access to amprenavir should they and their doctor(s) decide that it is a useful option. Since there have not been sufficient studies of amprenavir in "heavily pre-treated" PHAs, it is not clear how useful this drug will be for PHAs in need of rescue or salvage therapy. Drug interactions Like many drugs, amprenavir and other PIs are broken down and processed (metabolised) in the liver. The liver is able to metabolize these drugs because it has a series of enzymes called cytochrome p450. Taking amprenavir with another drug(s) that is also metabolized by the same enzymes can affect levels of each drug in the blood. As a result, levels of some drugs may increase, intensifying pre-exisiting side effects or causing new side effects; or levels of some drugs may decrease, resulting in no benefit from the drugs. Amprenavir can increase the level of the following drugs in the blood:
Warning - Drugs not to take with amprenavir Amprenavir should not be used with the following drugs:
The liquid formulation of amprenavir contains a chemical called propylene glycol. Users of amprenavir liquid should therefore not use the following medications because of the likelihood of side effects:
Serious or life-threatening drug interactions could occur if amprenavir is used with certain medications. However, sometimes people must take these medications. If amprenavir is taken with the following medications, doctors need to regularly check levels of these medications in the blood:
. Amprenavir contains a great deal of vitamin E; the full adult dose supplies about 1,750 international units/day. Therefore, users of amprenavir should not take additional vitamin E, as this can increase the risk of bleeding. Warning - Other health conditions Liver disease: Because amprenavir is processed by the liver, those people with liver damage may not be able to break down the drug in a normal time span. As a result, levels of amprenavir in the blood may rise to higher-than-normal levels. If this happens, the dose of amprenavir may have to be reduced. Severe kidney damage: As amprenavir liquid contains a large amount of propylene glycol, PHAs who have severe kidney damage are at increased risk of side effects if they use this formulation of amprenavir. Warning - Special populations If you are female or of Asian or Aboriginal origin, you may be at increased risk of side effects from the large amount of propylene glycol in amprenavir liquid formulation. Pregnant women: Women who are pregnant should not use amprenavir (capsules or liquid) as this drug can damage the fetus. Children: In Canada, amprenavir is not licensed for use in children under the age of 12. If for some reason children are prescribed the drug, those under the age of 4 years should never receive the liquid form of amprenavir. Liquid amprenavir contains a chemical called propylene glycol and this is toxic for children younger than 4 years. Resistance and cross-resistance Over time, as new copies of HIV are made in the body, the virus can change its structure. These changes are called mutations and can allow HIV to resist the effect of HAART. Combining amprenavir with at least two other anti-HIV drugs delays the development of resistance by HIV. To reduce the risk of developing resistance, all anti-HIV drugs should be taken every day as prescribed. The strict schedule for taking amprenavir is necessary because resistant virus can develop if levels of amprenavir fall too low. This may happen if doses are delayed or skipped. Levels of amprenavir can also become low due to certain drug interactions (previously listed). When HIV becomes resistant to amprenavir it also becomes resistant to ritonavir. This effect is called cross resistance. Should HIV develop resistance to amprenavir there are possible treatment options. The PI ritonavir (Norvir) can be used with the other protease inhibitors listed below to boost and maintain levels of the other protease inhibitor. Ritonavir in these formulations does not have antiviral activity. Its sole purpose in these combinations is to boost and maintain the levels of the other protease inhibitors. Here are some possible treatment options for amprenavir-resistant HIV:
Indication In March 2001, amprenavir was approved for use in combination with other anti-HIV drugs for the treatment of HIV/AIDS in Canada in adults and adolescents over the age of 12 years who have previously used protease inhibitors. Dosage Amprenavir is available in capsules and as a liquid. The recommended dose of amprenavir capsules for adults and adolescents greater than 12 years of age is:
Amprenavir may be taken with or without
food. However, do not take amprenavir with a high-fat meal as this
reduces the absorption of the drug.
Availability Amprenavir is available with a prescription. The manufacturer is negotiating with Canada's provinces and territories to have amprenavir paid for by their formularies. This information was provided by the Community AIDS Treatment Information Exchange (CATIE). For more information, contact CATIE at 1-800-263-1638. |
| Updated July 13, 2004 |
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