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Doctor Responds to PrEP User Tested Positive for HIV

Truvada Pills

Despite taking Truvada, a man was tested positive for HIV. What does it mean for PrEP and its effectiveness?

A gay man contracted HIV despite taking his daily doses of Truvada, it was reported at last week's Conference on Retroviruses and Opportunistic Infections (CROI).

Until then, the pill had been praised as highly effective, and was just approved by Canada as an acceptable HIV treatment. It's also prescribed as a pre-exposure prophylaxis (hence the acronym PrEP).

The concept behind PrEP is that if a patient adheres to the medication--takes it daily and as prescribed--the chances of contracting HIV are greatly diminished. Yet, in addition to the precaution of taking Truvada, physicans and researchers still encourage the use of condoms during intercourse.

Since the discovery of this new case of infection, the community has been asking whether Truvada-resistant strains of HIV can occur. Dr. David Knox, a Toronto based physican who treated the man who contracted HIV despite his daily dose of Truvada, spoke to Gawker about the siginificance of this anomaly, and talked about his findings related to Truvada (PrEP) use:

"I wouldn't let this single case of PrEP failure discourage anybody who's on PrEP or who's considering PrEP," Knox says. "Clearly, it works. There is robust data out there that suggests PrEP works the majority of the time. This is just a single case. The next steps really are to monitor the rate at which these mutations do occur. But PrEP's evolving, too. In a couple of years from now, we could be using injectable medication. I don't feel like this one case should discourage anybody to use PrEP if it's right for them."

A major question peppering conversations about PrEP is how to measure adherence and ensure that the subjects are taking the medication as prescribed. Without adherence, there no clear way to measure efficacy. Dr. Knox and his colleagues agreed that the man involved in this case was completely adherent:

"I think the reason why this case made it to CROI, which is by far the largest HIV conference in the world, and the reason why it got airtime is because this was the first case where we rigorously documented several lines of evidence pointing to the fact that this patient was adherent to the medication. While we think it's possible that this has happened in the past, that's the reason why this case got so much traction in the medical community."

Dr. Knox added:

"You can always call into question the patient's adherence. Even in cases of directly observed therapy, where you're watching the patient swallow the pill, you don't know what happens when that patient leaves the room. Adherence is a very, very tricky issue in clinical trials. There will always kind of be that question, which is why we had to go one step further in this case and collect the patient's pharmacy records and do the dried blood spots and make sure there was medication in his blood prior to his knowledge of his HIV status. We had to line all those things up to really solidify this case and adherence."

Ultimately, PrEP users and those considering it as a preventative measure should take this case with a grain of salt. Dr. Knox and those who presented the case at CROI believe the subject's case isn't completely indicative of the future, but adherence to Truvada is necessary for the medication's effectiveness.

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Nicholas Richard Rees