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How effective is PEP?

Jul 26, 2008

Dear Doctor Bob:

How effective is PEP after a insertive vaginal sex where the condom broke. I was started at the 19th hour after exposure.



Response from Dr. Frascino

Hello Sudhir,

We know PEP can help to abort HIV infection following an exposure. Unfortunately, I cannot tell you exactly how effective, because there are far too many variables to consider for each individual case. These variables are related to both viral (viral strain, viral load, etc.) and host (immune integrity, concurrent infections, route of exposure, size of inoculum, etc.) factors. What I can tell you is that PEP efficacy is linked to how quickly it is begun after exposure. The sooner it's started, the more likely it is to be effective. If more than 72 hours have passed since exposure, PEP is no longer considered worth trying. PEP efficacy also depends on including the appropriate antiretroviral drugs in the PEP regimen. If the patient were exposed to a virus already highly resistant to the drugs in the PEP regimen, PEP would fail. Finally, I can also tell you that even when PEP is prescribed and taken appropriately, there are PEP failures. It is not 100% effective in preventing HIV infection. A prime example of that would be yours truly. You can read more about PEP in the archives.

Good luck with your treatment.

Dr. Bob

HIV Specialists in SFO

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