YOU ARE HERE:
Where antiretrovirals block HIV
see PDF for diagram
Nucleoside analogue reverse transcriptase inhibitors (NRTIs)
NRTIs are normally the basis or 'backbone' of any anti-HIV drug combination. NRTIs may also be called nukes. The NRTIs are:
- 3TC, lamivudine, Epivir™
- abacavir, Ziagen™
- AZT, zidovudine, Retrovir™
- Combivir™, ( 3TC and AZT)
- Kivexa™ (abacavir and 3TC)
- Trizivir™, (3TC, AZT and abacavir)
- d4T, stavudine, Zerit™, Zerit PRC™
- ddC, zalcitabine, Hivid™
- ddI, didanosine, Videx™, Videx EC™
- FTC, emtricitabine, Emtriva™
Common dual combinations of NRTIs that are used as a part of three or four drug combinations are: AZT/3TC (often given as a combined pill called Combivir™, 3TC/abacavir (often given in a combined pill called Kivexa™, d4T/3TC, AZT/ddI. Combinations that should be avoided are: d4T/AZT, d4T/ddC, d4T/ddI, 3TC/ddC and ddI/ddC. The combination of ddI with the nucleotide analogue tenofovir should only be taken in exceptional circumstances and avoided whenever possible.
The nucleoside analogue FTC (emtricitabine) is often used with the nucleotide analogue tenofovir (often given in a combined pill called Truvada™).
Trizivir™ is a combination tablet containing three nucleoside analogues (AZT, 3TC, abacavir).
Non-nucleoside reverse transcriptase inhibitors (NNRTIs)
An NNRTI is often taken with two NRTIs as an alternative to a protease inhibitor. NNRTIs may also be called 'non-nukes'.
Two NNRTIs are currently approved for use in the UK:
- efavirenz, Sustiva™
- nevirapine, Viramune™.
Nucleotide analogue reverse transcriptase inhibitors (NtRTIs)
Nucleotide analogues also work against reverse transcriptase, and are usually used in place of an NRTI in a three drug combination. One nucleotide analogue is approved in the UK:
- tenofovir, Viread™.
Tenofovir is also available in a combination tablet with the nucleoside analogue FTC (emtricitabine, Emtriva™) called TruvadaTM.
Protease inhibitors (PIs)
Protease inhibitors were the second class of antiretroviral drugs to be available on prescription. The protease inhibitors in current use are:
- amprenavir, Agenerase™
- fosamprenavir, Telzir™
- atazanavir, Reyataz™
- indinavir, Crixivan™
- lopinavir/ritonavir, Kaletra™
- nelfinavir, Viracept™
- ritonavir, Norvir™
- saquinavir hard gel and tablet, Invirase™
- saquinavir soft gel, Fortovase™
People who choose to take a combination containing a protease inhibitor often take a protease inhibitor 'boosted' by a small dose of ritonavir, as well as taking two NRTIs. Common 'boosted' protease inhibitors are: ritonavir/saquinavir, indinavir/ritonavir, lopinavir/ritonavir, amprenavir/ritonavir, atazanavir/ritonavir.
Other combinations may include one or two protease inhibitors, one NNRTI, and one or two NRTIs. If a person's initial combination has not worked, some doctors may recommend a combination of four or more antiretrovirals.
Fusion inhibitors
Fusion inhibitors stop HIV from binding to and entering the human cell. One fusion inhibitor called T20 (enfuvirtide, Fuzeon™) has been approved and is given by a subcutaneous injection (similar to the way diabetes inject insulin). It is only available to people who have been extensively pre-treated with other anti-HIV drugs and have very limited treatment options available to them.
- T-20, enfuvirtide, Fuzeon™