Low risk of resistance

The aim of HIV treatment is an undetectable viral load. However, if HIV isn’t fully suppressed then the virus can develop resistance to the drugs used to treat it. This can have an impact on the choice of drugs available to people. Before you start any new HIV treatment, you should have a resistance test to help ensure the drug is effective for you.

Modern HIV drugs are generally very powerful, easy to take and cause only mild side-effects. They are therefore associated with a lower risk of resistance than earlier generations of anti-HIV drugs.

Swiss researchers wanted to establish the risk of resistance associated with individual combinations of drugs.

All the combinations they looked at were based on either 3TC (lamivudine, Epivir) or FTC (emtricitabine, Emtriva). They were then grouped according to the other drugs taken in the combination.

Over six years, 16 per cent of people who were taking a combination that included both AZT (zidovudine, Retrovir) and efavirenz (Sustiva) developed resistance. This compared to between 5 and 9 per cent of patients treated with other combinations.

Two-thirds of all cases of resistance developed when patients had a viral load between 50 and 500 copies/ml.
The researchers think this finding is 'remarkable' and suggest that people who experience a low rebound in their viral load when taking treatment should be closely monitored for resistance.

The research underlines the effectiveness of modern HIV treatment. AZT is no longer recommended for routine long-term use in countries like the UK. But the findings of this study are important for low- and middle-income countries where AZT is a backbone of HIV treatment.