Doxy PEP or doxycycline (a well-known antibiotic) has been making headlines lately because of a new STD-related study. The findings are surprising and impressive at the same time. When taken after unprotected intercourse, Doxy PEP reduces the risk of sexually transmitted infections by about two-thirds.
These numbers sound amazing but what is there to know about taking antibiotics in an attempt to prevent sexually transmitted infections? Does Doxy PEP work against all bacterial STDs and in all populations? These important questions need to be answered before the potential treatment is taken a step further.
The Doxy PEP Study
During the 24th International AIDS Conference, the world found out that a doxycycline study among bisexual men and transgender women was discontinued prematurely because of the unexpectedly high efficacy rate.
All of the details on the Doxy PEP study are presented in the following report.
According to presenters at the International AIDS Conference, people given doxycycline after condom-free sex reduce their risk of contracting gonorrhoea, chlamydia or syphilis by 66 per cent.
Originally, the study was supposed to continue until May 2023. It was discontinued about one year prior to the end date because of the positive findings and the data collected by that point in time.
Study participants included 327 people on HIV pre-exposure prophylaxis (PrEP) and 174 HIV-positive individuals. As per the study requirements, all participants needed to have been born male and all of them should have had at least one STD over the course of the last year.
As per the latest study report, the interim findings showed efficacy so high that it negated the need to continue the clinical trial.
Efficacy in HIV-negative participants on PrEP was estimated at 66 per cent. Out of those participants, 61 contracted an STD in comparison to 82 people in the control group (the ratio of doxycycline-taking participants to placebo-taking participants was two to one). Efficacy was slightly lower among HIV-positive individuals – 62 per cent. Still, the number is significant enough to warrant conclusions about the high effectiveness of doxycycline as an STD prevention method.
Doxycycline Limitations
While the medical community is optimistic, there are significant limitations to Doxy PEP that must be acknowledged. A major clinical trial by University of Washington researchers highlighted these disparities when they assessed the protocol’s effectiveness among cisgender women.
The study followed 449 female volunteers taking daily HIV PrEP. Despite the regimen, there was no statistically significant difference in new infection rates between the Doxy PEP group and the control group. Researchers suspect that physiological factors, specifically how the drug accumulates in vaginal tissue compared to rectal tissue, contribute to this lack of efficacy in women.
Existing antibiotic resistance is another hurdle. The bacteria responsible for gonorrhoea have already developed significant resistance to tetracyclines in many populations. This pre-existing resistance likely explains why Doxy PEP is far less effective at preventing gonorrhoea compared to its high success rates with chlamydia and syphilis.
Balancing Innovation with Caution
Doxycycline was selected for this protocol because it is affordable, accessible and has a well-established safety profile from decades of use in malaria prevention. However, transforming a treatment drug into a daily or weekly preventative measure requires careful consideration.
The primary concern amongst healthcare professionals is antibiotic stewardship. There is a valid fear that routine administration of doxycycline could pressure bacteria into developing resistance, eventually rendering the drug useless for treatment.
Fortunately, current data distinguishes clearly between different infections. While gonorrhoea strains often display resistance, studies show that chlamydia and syphilis bacteria remain highly responsive to doxycycline treatment. The goal is to monitor this closely to ensure these condition remain treatable.
Also, keep in mind that new products like Doxy PEP are only effective in the prevention of bacterial STDs. Viral conditions like HIV, hepatitis and genital herpes are also a significant risk that cannot be underestimated.
If you have questions about prevention and prophylaxis, get in touch with healthcare professionals like the Shim Clinic team. You can pay us a visit during working hours every day of the week or contact Shim Clinic to have your questions answered.