Pre-Exposure Prophylaxis or PrEP

Pre-exposure prophylaxis (PrEP) involves putting HIV negative people on antiretroviral drugs (ARV) with the aim of protecting them from HIV infection. This blog looks at some of the pros and cons of PrEP.

Monday, February 28, 2011

Maximizing Profits from a Drug that Doesn't Work

Advocates of PrEP are probably as aware as anyone else that it hasn't yet shown much promise for men who have sex with men (MSM). It may not even be of much use in combination with other strategies (that also haven't shown much promise). But no one really wants to be the first to say that there is still a lot left to do, or admit that PrEP may end up in the broom cupboard.

Advocates still go back to their tack of 'sub-group analysis', taking the group that shows the best level of adherence to the drug and pointing out how effective it was for them. But high levels of adherence to PrEP could indicate other protective and risk avoidence practices, so care needs to be taken in interpreting this.

More importantly, levels of adherence in the group that shows the lowest levels of adherence could indicate that they engage in other risk behaviors and fail to take protective measures, adhering to PrEP just being one. Dr Joseph Sonnabend has discussed the folly of such analyses.

So these advocates of PrEP gathered around the ashes to figure out what to do and one of the questions they came up with was "what subset of men would be the most appropriate candidates for this new prevention tool?" Sonnabend's warning against sub-group analysis recommends an 'intention to treat analysis' as an alternative.

However, PrEP on an intention to treat basis would mean they would aim to put all MSM on the drugs. And then you have the problem that you will spend a lot of money for a miniscule return (if any). Even UNAIDS will start to notice if the effectiveness of PrEP doesn't improve considerably.

The group of advocates conclude that "PrEP is not a “magic bullet” and that it should not be viewed as the sole approach to reducing new HIV infections among MSM".

Exactly; they've also got a brand new roll of sticky tape, a stapler, a needle and some thread, a pot of glue and some thumb tacks, otherwise known as 'treatment 2.0'. So maybe they won't need the PrEP after all.


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