Avoiding STIs: Doxycycline as post-exposure prophylaxis?
A recent study investigated whether the incidence of sexually transmitted infections can be reduced by post-exposure administration of doxycycline.
Can the effects of doxycycline help in STI prevention?
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The study was conducted with 501 participants who were either taking pre-exposure prophylaxis against HIV or living with HIV and had gonorrhoea, chlamydia or syphilis in the last 12 months.
- It was based on a 2:1 randomisation for 200 mg doxycycline within 72 hours of unprotected sex or no administration of the drug.
- The administration of doxycycline was able to reduce the incidence of syphilis, gonorrhoea and clamydia by two-thirds.
STIs: A problem for vulnerable groups
Sexually transmitted infections can affect anyone and everyone. Often, simple treatment by the family doctor or gynaecologist is enough, although the same does not always apply to risk groups. Especially for people living with HIV, an infection can sometimes have serious consequences.
Homosexual men and transgender women are still among the people who - at least in the western world - most frequently contract HIV and STIs. Experts have therefore been discussing for some time which methods make sense to limit transmission.
The antibiotic as a beacon of hope
The question of post-exposure prophylaxis is particularly interesting. After all, an infection can possibly be avoided in this way and the person affected does not get sick in the first place.
Doxycycline is considered a top candidate for this task. The antibiotic has long been used in the treatment of STIs and is usually well tolerated. A recent study has now investigated whether the drug is also effective as a post-exposure prophylaxis.
Doxycycline administration, or wait and see
The authors conducted their study in a 2:1 randomisation. Key details included:
- 501 participants: all were MSM or transgender women.
- All were either taking pre-exposure prophylaxis (PrEP) against HIV, or were already living with the virus.
- Inclusion criterion was a diagnosis of gonorrhoea, chlamydia or syphilis in the last 12 months.
- 2:1 randomisation: either 200 mg doxycycline within 72 hours of unprotected sex or standard treatment (no doxy).
- Quarterly screening for STIs.
Significant reduction in infections
The results are clear: while in the standard group without doxycycline 31.9% of patients with PrEP against HIV and 30.5% of those with HIV suffered an STI, this was the case in only 10.7% and 11.8% of participants in the doxycycline group, respectively. The results were statistically significant.
The antibiotic was well tolerated overall with only five cases of side effects (grade 3) and no serious side effects.
Doxycycline as effective STI prophylaxis
Post-exposure administration of doxycycline can significantly reduce the risk of sexually transmitted infections in men who have sex with men and transgender women. Overall, the intervention was well tolerated. The reduction in incidence for STIs is significant and postexposure prophylaxis should therefore be considered.
- Luetkemeyer AF, Donnell D, Dombrowski JC, Cohen S, Grabow C, Brown CE, Malinski C, Perkins R, Nasser M, Lopez C, Vittinghoff E, Buchbinder SP, Scott H, Charlebois ED, Havlir DV, Soge OO, Celum C; DoxyPEP Study Team. Postexposure Doxycycline to Prevent Bacterial Sexually Transmitted Infections. N Engl J Med. 2023 Apr 6;388(14):1296-1306. doi: 10.1056/NEJMoa2211934. PMID: 37018493; PMCID: PMC10140182.