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Journal Club: Acceptability and behavioural effects of antibiotic prophylaxis for syphilis prevention

Article reviewed

Farley TA, Cohen DA, Kahn RH et al. The acceptability and behavioural effects of antibiotic prophylaxis for syphilis prevention. Sex Transm Dis. 2003 Nov;30(11):844-9.

Pubmed link to abstract: http://www.ncbi.nlm.nih.gov/pubmed/14603093

Purpose of the study

Local epidemics of syphilis continue in North America despite continued efforts by public health agencies to control syphilis. The current approach has primarily been curative treatment and post-exposure treatment of sexual contacts.

The goal of the study was to assess the acceptability of pre-exposure prophylaxis among persons at high risk for syphilis. Pre-exposure prophylaxis is generally defined as treatment given before exposure to prevent disease; however, the authors included selected mass treatment and targeted presumptive treatment in the definition. Reluctance to adopt prophylaxis has been attributed to concerns of subsequent increases in risky sexual behaviour and in turn, increases in other sexually transmitted infections. To address this concern, the study also aimed to assess sexual behaviour after the implementation of antibiotic prophylaxis.


The study was a prospective cohort study that was not controlled, randomized, or blinded.

Participants were recruited through a mobile community-screening clinic that serviced neighbourhoods with a high-prevalence of STDs in Louisiana. Clients of this clinic were eligible if they were 18 to 49 years old and had 3 or more sexual partners in the last 6 months. Participants completed a questionnaire about sexual behaviours and had baseline testing for gonorrhea, chlamydia and syphilis. Participants were excluded if serology was positive for syphilis. Eligible participants were offered a choice of the following regimens:

  1. 1 dose of benzathine penicillin 2.4 million units IM or
  2. 3 doses of azithromycin 1 g at time 0, 2 and 4 weeks (witness ingestion in the clinic)

Education on safe sexual practice was also provided. Follow-up occurred at 4 weeks and 4 months.


Of the 174 participants, 86% chose IM penicillin and 14% chose oral azithromycin. However, only 10% completed all 3 doses of azithromycin.

At the 4 month follow-up, 72% of participants were available for assessment.  The study found a statistically significant reduction in the self-reported number of sexual partners.  There was no significant change in condom use.  Ninety-five percent (95%) of participants indicated they would be willing to take antibiotic prophylaxis again (97% of the penicillin group; 80% of the azithromycin group). Eighty-one percent (81%) would be willing to take monthly prophylaxis.

Impact on clinical practice

This study concluded that antibiotic prophylaxis was acceptable and did not increase risky sexual behaviour. This study also suggests that penicillin injection may be an acceptable method, at least short-term.

The number of participants lost to follow-up was about 30% and may have biased the results, over-estimating acceptability. However, the results are supported by an observational study by Rekart et. al that assessed the impact of syphilis mass treatment in Vancouver one year later (2). Rekart et. al found an overall positive attitude towards mass treatment and no increase in risky sexual behaviour. Acceptability of chemoprophylaxis was found in a survey of gay men in Australia (3).

Although zero cases of syphilis were found at the 4 month follow-up period, the study excluded candidates positive for syphilis, thereby excluding those with higher-risks. The study did not assess for a rebound of syphilis, as was seen after mass treatment with azithromycin in Vancouver.

Future studies are needed to re-assess the acceptability of pre-exposure prophylaxis in the local population including sex trade workers, their patrons and men who have sex with men (MSM).  Higher quality, randomized placebo control studies are needed to assess whether medications and education versus education alone decreases syphilis rates given the risk for rebound rates and bacterial resistance.

Further information

  1. Rekart ML, Patrick DM, Chakraborty B et al. Targeted mass treatment for syphilis with oral azithromycin. Lancet. 2003 Jan 25;361(9354):313-4.
  2. Rekart ML, Wong T, Wong E et al. The impact of syphilis mass treatment one year later: self-reported behaviour change among participants. Int J STD AIDS. 2005 Aug;16(8):571-8.
  3. Wilson DP, Prestage G, Gray RT et al. Chemoprophylaxis is likely to be acceptable and could mitigate syphilis epidemics among populations of gay men. Sex Transm Dis. 2011 Jul;38(7):573-9.


Dr. Richard Lester, Medical Head, STI/HIV Control, Clinical Prevention Services, BCCDC
Avril Spencer, Clinical Nurse Educator, STI/HIV Control, Clinical Prevention Services, BCCDC