Rupert Whitaker: A pill for risky sex-another step on the road to a pill for bad housing

Published: November 7, 2014

Rupert Whitaker
Original Article:

PrEP—or chemoprophylaxis against HIV infection, as the less sexy phrase goes—is about using chemicals to prevent yourself from contracting HIV during sex or the sharing of injection equipment, the acronym standing for “pre-exposure prophylaxis.” It has gradually emerged as a possibility as a public health intervention after six years of clinical trials. It looks very promising, but only some of the problems that burden it are being discussed during the increasing—and increasingly irrational—hoopla around the topic.

The two chemicals in question are emtricitabine and tenofovir, both nucleoside/nucleotide reverse transcriptase inhibitors, combined in the product Truvada, which is used primarily as a medication for treating established HIV infection. That it’s Truvada as opposed to another product is not actually essential to the problems; the chosen drug will no doubt change over time, but Truvada is the exemplar for the moment.

There are usual and unusual concerns. Firstly, does it work? The short answer is yes. That is, in clinical trials. If you use it properly. If it’s part of a comprehensive service of prevention, including regular HIV testing, counselling, condom provision, and the diagnosis and treatment of (other) infections. In other words, it works in just the same way as condoms do in real life.

There has been a variety of studies showing its efficacy. The most effective trials raise questions around reporting on as treated vs. intention to treat (the latter reportedly showing lesser efficacy), as well as about sampling from highest risk populations, where efficacy is therefore inflated owing to high baseline risk, which also reduces one’s ability to extrapolate to a wider population. Still, it would be unwise to attempt to claim that PrEP is not efficacious to some degree. Two more recent, European studies (PROUD and IPERGAY), using very different dosing approaches, have been terminated early owing to clear evidence of efficacy. Yet, as the medical journalist Gus Cairns has noted, the closure of trials of efficacy does not mean that the questions are all answered.

The primary problem with PrEP is that, firstly, just as with HIV medications and condoms, it would not necessarily be delivered as part of adequate services in the clinic and, secondly, we don’t always use them properly, sometimes for very good reasons. In real life, physicians won’t always be compliant with guidelines that require PrEP to be prescribed as part of even a minimal programme of behavioural health, and this will increase the risk of problems that are already well evidenced with both PrEP and HIV treatment, such as non-adherence and disengagement from services. The “cascade of care” for high risk HIV negatives will abruptly stop there.

The evidence of PrEP’s effectiveness in even the most rigorous epidemiological modelling of PrEP is predicated upon the continuation of the same level of condom use in at risk populations. Jean-Michel Molina, principal investigator of the IPERGAY trial, is reported to have said that “condoms remain the cornerstone of HIV prevention.” Yet, while a great deal of effort is going into promoting PrEP, little is going into promoting other methods or even combined prevention—at the same time as services are doing away with even low competence health advising, in tandem with the rise of over the counter HIV testing kits.

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