Study identifies characteristics of gay men who may be suitable for intermittent PrEP

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Older, better-educated gay men who use sexual networking sites and have sex outside the context of committed relationships may be appropriate targets for intermittent pre-exposure prophylaxis (PrEP), US research published in the online edition of the Journal of Acquired Immune Deficiency Syndromes suggests.

The investigators found that individuals with this profile were more likely to plan their sexual encounters and to have anal sex fewer than three times per week.

“Our study serves to better characterize MSM [men who have sex with men] who may most benefit from event-based intermittent PrEP,” comment the authors.


event based

In relation to pre-exposure prophylaxis (PrEP), this dosing schedule involves taking PrEP just before and after having sex. It is an alternative to daily dosing that is only recommended for people having anal sex, not vaginal sex. A double dose of PrEP should be taken 2-24 hours before anticipated sex, and then, if sex happens, additional pills 24 hours and 48 hours after the double dose. In the event of sex on several days in a row, one pill should be taken each day until 48 hours after the last sexual intercourse.

risky behaviour

In HIV, refers to any behaviour or action that increases an individual’s probability of acquiring or transmitting HIV, such as having unprotected sex, having multiple partners or sharing drug injection equipment.

The iPrEX study involving gay and other MSM showed that PrEP significantly reduced the risk of acquiring infection with HIV.

However, adherence is a major barrier to the success of PrEP. There are also concerns about its cost and potential side-effects. Intermittent dosing has been proposed as a way of overcoming these limitations. A recently published study showed that adherence was also challenging when an intermittent dosing strategy was used.

This treatment strategy involves taking a dose of antiretroviral therapy before a risky sexual encounter, with a second dose taken shortly after.

This strategy will only be suitable for people who engage in risky sex fewer than three times per week, and who plan their sexual encounters.

Investigators in the US wished to establish a better understanding of the characteristics of gay men and other MSM who fulfilled these criteria.

HIV-negative gay men were recruited to the study using social networking sites in late 2010. All were sexually active (defined as anal sex within the previous month). The men supplied demographic data, as well as information about their sexual risk behaviour, how they planned their sexual encounters, their use of sexual networking media and their relationship status.

A total of 1013 men participated in the research. Their median age was 28 years. Most (56%) participants reported that their last anal sex was unprotected.

When asked about their sexual activity in the previous week, 49% of men reported that they had had no sex, 27% said they had had sex once and 9% reported sex on two days. The remaining 15% of men said they had had sex on three or more days.

Half the men reported that their last sexual encounter involved no advance planning, and for 8% of men planning consisted of a few minutes notice before the event. The remaining men reporting planning sex hours (22%), one to three days (11%), or more than three days (8%) in advance.

In all, 31% of men reported both less frequent sex and planning sex and were therefore potential candidates for intermittent PrEP.

Factors associated with less frequent sex and its planning were older age (median 30 vs 27 years, p < 0.001), higher likelihood of completing a college education (46 vs 32%, p < 0.001), an HIV test within the past twelve months (54 vs 47%, p = 0.033), use of sexual networking sites at least once a week (55 vs 44%, p = 0.001) and last sexual encounter with a non-committed partner (60 vs 38%, p < 0.001).

“Additional knowledge regarding sexual frequency and planning will be crucial in identifying MSM who may benefit from this intervention [intermittent PrEP]”, conclude the investigators. “With use of tenofovir/FTC as PrEP, daily dosing will still remain necessary for the majority of high-risk MSM who report more frequent sexual activity or less planning.”


Volk JE et al. Sexual frequency and planning among at-risk men who have sex with men (MSM) in the US: implications for event-based intermittent pre-exposure prophylaxis (PrEP). J Acquir Immune Defic Syndr, online edition. DOI: 10.1097/QAI.0b013e31825bd87d, 2012.