A study has shown that resistance to Tenofovir is increasing worldwide, which raises concerns about the drug which is critical for HIV treatment and prevention

A Tenofovir tablet
A Tenofovir tablet

The study, published online in The Lancet Infectious Diseases, followed 1,926 people in 36 countries who continued to have uncontrolled HIV despite taking treatment. The results showed that the number of people, which are limited to people who were experiencing problematic uncontrolled viral loads, with tenofovir-resistant HIV ranged from 20 percent in Europe to over 60 percent in sub-Saharan Africa.

Tenofovir has been the go to drug for both treating and preventing HIV for a number of years. It is often better known in it’s co-formulated (with Emtricitabine) form, Truvada.  It can also be used to treat hepatitis B.

“If you develop resistance to that, it’s a very large loss,” said study author Dr. Robert Shafer, of Stanford University in California.

“People acquire HIV resistance to Tenofovir in one of two ways”, he said. “Either they don’t take the drug as intended and the virus mutates, or they are infected by someone with a resistant form of the virus.”

The study isn’t able to say why we have Tenofovir resistance to begin with but the research found that people who started taking Tenofovir with a low CD4 count were about 50 percent more like to develop Tenofovir resistance than those who started with a higher CD4 count.

Combining Tenofovir with certain other drugs can also increase the chance of resistance developing. Notably those taking lamivudine (instead of emtricitabine) or nevirapine (instread of efavirenz) were up to 50 percent more likely to develop Tenofovir resistance.

Dr. Ravi Gupta, of University College London, said that we need to monitor both how well people are taking their treatment, and monitor resistance levels if we’re to avoid this problem becoming much worse. “We need these early warning systems and to act on what we find”

“I think that if these trends continued . . . and you found a lot of HIV infections had resistance, then you would find the efficacy of PrEP is compromised, The availability of second-line drugs is increasing, but they’re quite a bit more expensive and have more side effects associated with them,”


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  1. I object to an article about Tenofovir being ineffective displaying a picture of Truvada as it’s lead graphic.


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