Friday, 13 September 2013

Oral antiretroviral pre-sexual exposure HIV prophylaxis, causes for concern

Sexual contact is the most common route of HIV transmission* whose rate of infection after a sexual contact varies according to the nature of the contact and whether it is protected or not and the HIV subtype. The search for potential vaccines has yielded little result. Oral antiretrovirals, life saving drugs for HIV-infected patients, have a role to play among other means in the prevention of sexually transmitted HIV infection in at-risk HIV negative populations. In this context, they are used for pre-sexual exposure prophylaxis (PrSEP), post-sexual exposure prophylaxis and early treatment of the HIV-infected partners. Other means include topical antiretrovirals, male circumcision and male/female condoms. Certainly abstinence is the definitive way for prevention of any sexually transmitted infection. Pre-exposure prophylaxis that is shown to be effective in reducing HIV transmission in one population may not necessarily work in other at-risk populations, hence the conduction of trials in different population groups representing different routes of HIV transmission, including heterosexuals, MSM, and injecting drug abusers.

The concept of providing pre-exposure prophylaxis is not new. Apart from vaccines, a famous example is the pre-exposure prophylaxis against malaria for travellers to endemic areas. Theoretically, if HIV replication is inhibited from the moment the virus enters the body, it may not be able to establish a permanent infectionPrSEP has been shown to reduce the risk of HIV infection among adult men and women at high risk for HIV infection through sex.  The FDA has approved the combination medication tenofovir disoproxil fumarate plus emtricitabine for use as PrSEP among sexually active adults at risk for HIV infection. At-risk populations such as MSM are not necessarily aware of the presence of PrSEP. However, knowledge about this role of oral antiretrovirals may have effect on willingness to accept it. Serodiscordant couples have been advised of early treatment for the infected partner, PrSEP for the uninfected partner, or a combination of the two. PrSEP might be an effective prevention method for women who are unable, for whatever reason, to negotiate condom use. PrSEP might also be used as a risk reduction strategy for HIV negative women who request to conceive naturally from HIV positive men via timed unprotected sex, PrSEP for conception (PrSEP-C). 

It should be noted however that PrSEP can give a false sense of security that might lead to easier transmission of other sexually transmitted infections.  Moreover, continued use of a PrSEP regimen in the presence of undiagnosed HIV infection is analogous to the HIV monotherapy or dual therapy strategies used in the early stages of the HIV epidemic. Such regimens are known to carry an unacceptably high risk of HIV drug resistance, with important clinical implications for the patient and public health implications for the sexual partners. Extensive studies are needed to address the safety concerns associated with use of daily oral PrSEP in HIV negative people, whether in long or short term courses, and to address cost concerns of PrSEP and feasibility to deliver it.

*National statistics show injection drug use is the principal mode of HIV transmission in Iran.

This page was last updated in October 2013.

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Main Works of Reference List (The first eight are my top favourites)

  • British National Formulary
  • British National Formulary for Children
  • Guidelines (BAD - BASHH - BHIVA - Uroweb)
  • Oxford Handbook of Genitourinary Medicine, HIV, and Sexual Health
  • Oxford Handbook of Medical Dermatology
  • Rook's Textbook of Dermatology
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