Postexposure prophylaxis does not lead to an increase in high-risk behaviour

Graham McKerrow HIV, i-Base

Postexposure prophylaxis (PEP) consisting of antiretroviral medication and behavioural counselling following a potential sexual exposure to HIV does not lead to an increase in high-risk behaviour in most people, according to researchers in San Francisco.

Jeffrey N Martin and colleagues conclude that their findings of “this lack of behavioural disinhibition” coupled with prior safety and feasibility data suggest that the use of PEP should be routinely considered following high-risk sexual exposures.

The researchers conducted a non-randomised trial of 397 adults with high-risk sexual or drug-use exposure within the previous 72 hours. The intervention consisted of antiretroviral medication for four weeks and five counselling sessions. Participants were followed for 12 months to record repeat requests for PEP, modifications to high-risk behaviour and the acquisition of STDs and HIV.

The majority of participants (83%) did not request a repeat course of PEP. Seventy-three percent reported a decrease compared to baseline in the number of times they performed high-risk sexual activities, 13% reported no change and 14% reported an increase. Most, (85%) had no change in the incidence of STDs, 8.5% had a decrease and 6.8% an increase. Three gay men seroconverted for HIV, none of which was associated with the presenting exposure; this represented a rate of 1.2 per 100 person years and was similar to rates in San Francisco for all gay men.

In their discussion the authors write: “Direct proof of the efficacy of non-occupational PEP in preventing HIV transmission is still needed. Although we saw no instances of chemoprophylactic failure, we would not have necessarily expected to observe any HIV seroconversions associated with the presenting exposures even without the provision of PEP, given our sample size, the low per-exposure infectivity of HIV and the likelihood that some participants had contact with uninfected sources. Therefore, our data should not be taken as evidence for the efficacy of PEP in preventing seroconversion. Unfortunately, definitive ascertainment of the efficacy of PEP following a sexual exposure through randomised placebo-controlled trials will be difficult because of the large sample size required. Until direct evidence regarding efficacy is available, decisions must nonetheless be made on how to manage individuals with high-risk sexual exposures. Given the indirect evidence of efficacy gleaned from the occupational setting and from animal studies, coupled with our findings on feasibility and safety, we believe that PEP, comprising both antiretroviral medication and risk-reduction counselling, should be routinely considered following high-risk sexual exposures.”


Martin JN, Roland, ME, Neilands T et al. Use of postexposure prophylaxis against HIV infection following sexual exposure does not lead to increases in high-risk behavior. AIDS :Volume 18(5) 26 March 2004 pp 787-792.

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