Mark O'Reilly

Clinical posts from members and guests of the Australasian Society for HIV, Viral Hepatitis and Sexual Health Medicine (ASHM) from various international medical and scientific conferences on HIV, AIDS, viral hepatitis, and sexual health.


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 Comment: Abstract follows.

For me, this was one of the most interesting studies presented at CROI this year. It generated much discussion amongst delegates and took the post, rather than pre-exposure prophylaxis approach.

STI antibiotic prophylaxis is a topic thats been discussed for decades. Were all struggling to manage the rapid increase in STIs over the past two to three years. Risk compensation is alive and well and our many of our MSM patients frequently present between routine HIV or PrEP visits with symptomatic STIs.

As per my previous blog, the evidence to date for STI antibiotic prophylaxis is limited and the potential costs are high. Of some concern is that antibiotic resistance testing in this study, only pertains to STIs and not other relevant organisms such as malaria and those causing serious skin and respiratory infections.

 The abstract is listed below but Ill end with Jean Michels conclusion slide:

 - PEP with doxycycline reduced the overall incidence of bacterial STIs by 47% in MSM on PrEP (8.7 months of PFU).

- No effect on Gonorrhoea but strong reduction (70-73%) in Chlamydia and Syphilis incidence.

- Acceptable safety profile with mild/moderate GI A/Es leading to discontinuation in only 7% of participants.

- No evidence of risk compensation.

- Analysis of antibiotic resistance pending (STIs only).

- Long term benefots of PEP yet unknown.

- Antibiotic prophylaxis for STIs still NOT RECOMMENDED.

- More research needed in the field of STIs.



Jean-Michel Molina et

Background: A high incidence of bacterial sexually transmitted infections (STIs) has been reported in several PrEP trials and demonstration projects among MSM. We wished to assess whether on demand post-exposure prophylaxis (PEP) with doxycycline could reduce STIs incidence in this high risk group.

Methods: High risk adult MSM being followed in the open-label phase of the ANRS IPERGAY trial with on demand TDF/FTC for HIV prevention, were enrolled in a prospective randomized open-label sub-study. Participants (pts) were randomized 1:1 to take either two pills of doxycycline (100mg per pill) within 72h after condomless sexual intercourse (without exceeding 6 pills per week) or no PEP. All subjects received risk-reduction counseling and condoms, and were tested every 8 weeks for HIV and STIs with serologic assays for HIV and syphilis and PCR assays for Chlamydia trachomatis and Neisseria gonorrhoeae in urine samples, oral and anal swabs. The primary study endpoint was the time to a first bacterial STI: gonorrhoea, chlamydia infection or syphilis. We compared the two study arms according to the intention-to-treat principle. We used time-to-event methods, including KaplanMeier survival curves and Cox proportional-hazards models.

Results: From July 2015 to January 2016, 232 pts were randomized, 116 in each arm. Median follow-up was 8.7 months (IQR: 7.8-9.7). Seventy-three pts acquired STIs during the study period, 28 pts in the PEP arm (24%, 37.7 events per 100 pt-years) as compared to 45 pts in the no PEP arm (38.8%, 69.7 events per 100 pt-years) for a hazard ratio (HR) of 0.53 (95% CI: 0.33-0.85, P=0.008). HR for gonorrhoea, chlamydia infection and syphilis were 0.83 (95% CI: 0.47-1.47, p=0.52), 0.30 (95% CI: 0.13-0.70, p=0.006) and 0.27 (95% CI:

0.07-0.98, p<0.05), respectively. Overall 71% of all STIs were asymptomatic. Pts in the PEP arm used a median of 7 pills/month (IQR: 3-13). Safety was good with only 8 pts (7%) discontinuing PEP because of gastro-intestinal adverse events (AEs). Gastrointestinal AEs were reported in 61 pts (53%) and 47 pts (41%) in the PEP and no PEP arms, respectively (p=0.07). There was no significant change in sexual behaviour between study arms during follow-up.


Conclusion: On demand PEP with doxycycline reduced the incidence of chlamydia infection and syphilis in high risk MSM and has an acceptable safety profile. The long-term efficacy of this strategy and its impact on antibiotic resistance needs to be assessed.

Tagged in: CROI 2017
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