ANTIRETROVIRAL TREATMENT OF HIV

This is the main type of treatment for HIV or AIDS. It is not a cure, but it can stop people from becoming ill for many years. The treatment consists of drugs that have to be taken every day for the rest of someone's life. To understand more about treatment you need to have some knowledge of HIV and AIDS.

HIV is a virus and like other viruses when it is in a cell in the body it produces new copies of itself. With these new copies, HIV can go and infect other previously healthy cells. It is easy for HIV to spread quickly through the billions of cells in the body, if it is not stopped from reproducing itself. Antiretroviral treatment for HIV infection consists of drugs which work against HIV infection itself by slowing down the reproduction of HIV in the body. The drugs are often referred as:

• antiretrovirals

• anti-HIV drugs

• or HIV antiviral drugs

For antiretroviral treatment to be effective for a long, it has been found that you need to take more than one antiretroviral drug at a time. This is what is known as Combination Therapy. The term Highly Active Antiretroviral Therapy (HAART) is used to describe a combination of three or more anti-HIV drugs.

The general recommendation is to use a minimum of two antiretroviral drugs. If one drug is taken on its own, it has been found that, over a period of time, the drug stops working. HIV reacts to the drug in the person's body and changes, so that the virus is no longer affected by the drug. The virus then starts to reproduce itself the same way as before. This is known as the virus becoming resistant to the drug. If two or more antiretrovirals are taken together it vastly reduces the rate at which resistance develops.

When a person's immune system is damaged by HIV, then certain infections or cancers will develop which the body would normally "fight off" quite easily. These are known as Opportunistic Infections. Treatment for Opportunistic Infections is usually provided when antiretrovirals are not available, or when the antiretrovirals drugs are no longer effective as the person is resistant to them.

There are four main groups of anti-HIV drugs. Each of these groups attacks HIV in a different way.

Nucleoside Reverse Transcriptase Inhibitors

The first group of antiretroviral drugs are the Nucleoside Reverse Transcriptase Inhibitors (NRTIs). They were the first type of drug available to treat HIV infection in 1987 and are better known as nucleoside analogues or nukes. HIV needs an enzyme called reverse transcriptase in order to be able to infect healthy cells and reproduce itself in a person's body. As the name says, NRTIs inhibit reverse transcriptase. The drugs slow down the production of the reverse transcriptase enzyme and make HIV unable to infect cells and duplicate itself.

Non-Nucleoside Reverse Transcriptase Inhibitors

The second group of antiretroviral drugs is the Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTIs). These drugs started to be approved in 1997 and are generally referred as non-nucleosides or non-nukes. This group of drugs also stops HIV from infecting cells by intervening with the trancriptase of the virus. The non-nucleoside drugs work slightly differently from the nucleoside analogues in that they bind in a different way to the cell's reverse transcriptase. The non-nucleoside drugs block the duplication and the spread of the HIV.

Protease Inhibitors

The third type of antiretroviral is the Protease Inhibitor (PI) group. They were first approved in 1995. Protease inhibitors, as the name says, inhibit protease. Almost every living cell contains protease. Protease is a digestive enzyme that breaks down protein and is one of the many enzymes that HIV uses to reproduce itself. The protease in HIV attacks the long healthy chains of enzymes and proteins in the cells and cuts them into smaller pieces. These infected smaller pieces of proteins and enzymes continue to infect new cells. The protease inhibitors take effect before the protease in HIV has the chance to break down the protein and enzymes. This way the protease inhibitors slow down the duplication of the virus and thus prevent the infection of new cells. The NRTIs and NNRTIs only have an effect on newly infected cells. Protease inhibitors are able to slow the process of immature non-infectious virus becoming mature and infectious. Protease inhibitors also work in cells that have been infected for a long time, by slowing down the reproduction of the virus.

Fusion or Entry Inhibitors

The fourth group of antiretroviral is called Fusion or Entry Inhibitors. These drugs have yet to be approved and are currently going through clinical trials in the UK and the USA. The surface of HIV carries proteins called gp41 and gp120. These are the proteins, which allow HIV to attach itself to, and enter into cells. By blocking one of these proteins, fusion inhibitors slow down the reproduction of the virus. For example, T-20, the fusion inhibitor that is closest to approval, sticks to the protein gp41. The T-20 fusion inhibitor differs from the other antiretrovirals in that it needs to be injected. T-20 is a protein and cannot be taken orally, since it would be digested in the stomach. It is hoped that the results from the T-20 trials across the USA and Europe will completed and returned to the Federal Drug Agency (FDA) by autumn 2002.

There are currently 15 approved antiretroviral drugs in the UK and many more in the expanded access programmes and trials. Each antiretroviral drug usually has three names. Sometimes drugs are referred by their research or chemical name, for example AZT. The second name for the drug is the common name for all the drugs with the same chemical structure, for example AZT is also known as zidovudine. The third name is the brand name given by the pharmaceutical company. One of the brand names for zidovudine is Retrovir.

The drug names listed here are those that are most commonly used or for salvage therapy. Those with * are not yet approved but available on an expanded access programme. This list does not contain new drugs that are currently under development and still in clinical trials. Further information should be available from your doctor.

Nucleoside Analogues (NRTIs)

Non-Nucleoside Reverse Transcriptase inhibitors (NNRTIs)

Protease Inhibitors (PIs)

Fusion or Entry inhibitors