An American study into using Truvada as PrEP has shown that the drug may not encourage people to take bigger risks in bed.

The iPrEx study, which lasted for three years, and involved 2,500 HIV negative people in six countries was designed to test the efficacy of Gilead Sciene Inc’s Truvada therapy in preventing HIV infection. The study  showed that the medication was more than 90% effective when it was taken as directed, the efficacy dropped dramatically when this wasn’t the case.

One of the biggest barriers to wide adoption of PrEP has been the concern that people would take bigger sexual risks due to the added perceived security afforded by the medication. “There has been a concern that really anything we do to prevent HIV in high-risk individuals could lead people to feel more secure and have riskier sex” said Dr Robert Grant from San Francisco’s Gladstone Institute of Virology and Immunology.

Grant and his team from Gladstone have now one back to the results and patient diaries to look at whether providing PrEP encouraged those involved in the study to increase their sexual risk taking.

The study data showed a 400% fall in new HIV infections amongst the cohort, as well as a drop in Syphilis cases. Dr Grant claimed that there was no evidence of an increase of sexual risk taking, and in fact there was data suggesting people adopting safer sexual practises.

Approximately 2,000 people in the USA, across various studies and trials, are taking Truvada as PrEP. Here in the UK gay and bisexual men who are HIV negative may be able to join the PROUD study, which is also working with the same drug, has 335 participants.

The paper from Gladstone was published in the Public Library of Science journal (PLOS ONE).


  1. I was doubtful when PrEP was first approved in the USA, as was my doctor (I was in hospital at the time and buttonholed her on the subject). You can see from articles I’ve written here that my thinking has changed. Truvada is far from perfect, but it, together with treatment as protection (ie maintaining an undetectable viral load) has proven to be superior to condoms as protection against transmission. And truvada is just the first drug, the proof of concept.

    I look forward to the refinement of the concept, using less “demanding” drugs, though it should be noted that we’re learning a lot about the action of truvada’s constituent drugs in the absence of HIV. If ou’re in easy reach of one of the trial centres in the UK and your last HIV test was negative (you do test regularly, don’t you?) please give serious consideration to joining the trial: they need 500 people, so there are 165 places still going…


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