Tuesday, May 17, 2011

Pre exposure prophylaxis for HIV

A homosexual male who is an iv drug abuser walks into the office...asking ways to help him prevent contacting HIV..with his high risk behaviour!! Apart from advising on safe sex and risks of sharing needles(which are most important..and at the same time cannot be relied at all times due to non adherence)....do we have any medications to offer him??

Lets look at the iPREX study published in NEJM Dec 2010. This was a placebo-controlled, double-blind, randomized trial involving 2499 subjects(men who have sex with men) to see if a combination of Emtricitabine-Tenofivir(FTC-TDF) once daily reduced the incidence of HIV over a f/u period of 1.2 years. Of the 100 incident HIV infections during the study period, 64 occurred in the placebo group and 36 in the FTC–TDF group, with an efficacy of 44% and a 95% CI of 15 to 63. An important finding to note is that, in the FTC–TDF group, the study drug was pharmacologically detected in 51% of subjects who remained free of HIV infection but in only 9% of those who became infected. So exposure to FTC–TDF was associated with a reduction in HIV acquisition. Main issues in putting this into practice has a few concerns. Few of them are drug adherence(very poor in the study), long term outcome, side effects(quite a few in the study drug group had renal impairement which rverted to normal on discontinuation of drug!). All these issues have been nicely discussed in the letter following the study( another arrow in the Quiver.NEJM Dec 2010)
Now the trial has been extended to look for long term outcomes and ways to improve adherence. results are expected by 2013.(HIV & TB News)

An earlier study , CAPRISA 004 in which a total of 889 sexually active, HIV-uninfected women (age range, 18–40) received either 1% tenofovir gel or placebo gel, with instructions to administer the gel intravaginally within 12 hours before sex and also within 12 hours after sex. Mean follow-up was 18 months.The incidence of HIV was 5.6 /100 person-years in the tenofovir group versus 9.1 /100 person-years in the placebo group, for an incidence rate ratio (IRR) of 0.61 (95% CI, 0.40–0.94; P=0.017). Shows promise for pre exposure prophylaxis.

In this context ...FEM-PrEP trial has to be mentioned. This study evaluated if oral daily FTC-TDF prevented HIV in a group of high risk women. The study was stopped last month after an interim analysis didnt find any benefit compared to placebo.(AVAC April 2011). Full analysis of trial should be available shortly.(may be related to adherence issues!!)

VOICE trial - Vaginal and Oral Interventions to Control the Epidemic .........is an ongoing study on high risk women comparing FTC-TDF, tenofovir tablet alone , or tenofovir gel. This study might shed light into ..which of these will be more effective. By this time we will also have the long term safety and compliance outcomes on the i-PREX study.
May be 2013 might be a year the world would see a...  'HIV prevention pill'  !!!


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