Standard anti-HIV treatment for people who are taking it for the first time will involve a combination, or "regimen," of three antiretrovirals. There are exceptions to this, for example if you are a woman and taking treatment when you are pregnant; or if you have a very high viral load and need to take more than three drugs to get a powerful anti-HIV effect.

Most British doctors think that it is probably best to start with a combination that involves a non-nucleoside reverse transcriptase inhibitor (NNRTI), or a "boosted" protease inhibitor.

This should be taken with a combination of two nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs). Either:

• tenofovir/FTC (available in a combination pill, Truvada)

• abacavir/3TC (available in a combination pill, Kivexa)

• AZT/3TC (available in a combination pill, Combivir)

However, AZT has been associated with body fat changes and your doctor should discuss the risks of these occurring, and side-effects which abacavir and tenofovir can cause, before you decide which drugs to take.

The anti-HIV drugs which are currently available on prescription in the UK, and the drug class to which they belong, are shown on the following page.

see PDF file for table: Anti-HIV drug names

Two nucleoside/nucleotide analogues plus one NNRTI

• If you are starting anti-HIV treatment for the first time, you are recommended to take a combination of two nucleoside/nucleotide analogues and one NNRTI.

NNRTIs appear to present fewer problems with side-effects than protease inhibitors. This, together with the potential for easier adherence, are the main reasons why many doctors choose NNRTI-based combinations for use in people starting anti-HIV treatment. Their major disadvantage is that it is very easy to develop drug resistance to an NNRTI drug, and if this happens, it is unlikely that you will benefit from any other NNRTI.

If you choose to take an NNRTI, efavirenz (Sustiva) is usually prescribed, unless you are a woman and thinking about becoming pregnant. An alternative is nevirapine (Viramune). To reduce the risk of potentially serious side-effects you should not start taking nevirapine if you are a man with a CD4 cell count above 400 or a woman with a CD4 cell count above 250.

Two nucleoside/nucleotide analogues plus a "boosted" protease inhibitor

• If you are starting anti-HIV treatment you may consider taking a combination of two nucleoside/nucleotide analogues and a "boosted" protease inhibitor.

“Boosted” protease inhibitors have a small amount of ritonavir added. This increases the blood levels of the protease inhibitor being boosted and may allow both fewer pills and fewer doses, which may improve your adherence. Boosted protease inhibitors may also have a stronger anti-HIV effect, and may be less vulnerable to the risk of drug resistance. The main disadvantages of protease inhibitor-based combinations are that they may have a higher risk of longer-term side-effects and be less easy to adhere to.

If you choose to take a boosted-protease inhibitor, it is likely that your doctor will recommend that you take lopinavir/ritonavir (Kaletra). Other options are saquinavir/ritonavir (Invirase 500mg) and fosamprenavir/ritonavir (Telzir). At the moment, there is not enough evidence for atazanavir/ritonavir (Reyataz) to be recommended for first-line therapy.

Three nucleoside/nucleotide analogues

A combination of three nucleoside/nucleotide analogues is not recommended, even if you have a low viral load. However, in some exceptional cases it may be considered.

Nucleoside/nucleotide backbone

It is not known which nucleoside/nucleotide backbone is the most effective. However because of concerns about side-effects, d4T is not recommended as part of your first-line therapy. There are also concerns that AZT can cause fat loss and it is currently recommended that AZT should not normally be considered for first-line therapy. If you are currently taking AZT you should be offered the chance of switching to abacavir or tenofovir.

AZT, abacavir and tenofovir all have side-effects, and these should be explained to you before any treatment decision is reached.

If you have hepatitis B virus infection as well as HIV, then you are recommended to take FTC/tenofovir, or 3TC as these drugs are active against both HIV and hepatitis B virus.