Doxycycline

Lymphogranuloma venereum (LGV) is a sexually transmitted infection (STI) caused by the L genotypes of C. trachomatis. Proctitis is the main clinical manifestation of infection in the current LGV epidemic. However, recent European studies reported that about 25% of the anal LGV infections are asymptomatic. In France, asymptomatic anal LGV increased from 36.1% (44/124) in 2020 to 52.4% (66/126) in 2022. LGV testing is recommended on all C. trachomatis-positive anorectal specimens because therapy of extended duration is required. Patients with anal C. trachomatis infection should be treated initially with 7-day course of doxycycline (200 mg per day orally) while awaiting the results of LGV testing. Treatment should be extended to 21 days in cases of LGV according to current European and USA guidelines for LGV treatment. This regimen is indicated for symptomatic and asymptomatic anorectal LGV, with a 98.5% treatment efficacy. However, there is no obvious biological basis for prolonged treatment of asymptomatic LGV. Three recent retrospective studies showed that a 7-day course of doxycycline was effective for the treatment of asymptomatic LGV, with microbial cure ranging from 97% (38/39) to 100% (54/54). The objective of this study is to evaluate the efficacy (microbiological cure rate) of a 7-day course of doxycycline 200 mg daily orally for the treatment of asymptomatic anal LGV infection, four weeks after treatment initiation.

The goal of this observational study is to understand the risk of antibiotic resistance and changes in the human microbiome (bacteria that live inside and on us), if people use antibiotics to prevent sexually transmitted infections (STI prophylaxis, doxycycline post-exposure prophylaxis, or 'doxyPEP'). The study will assess how easy and acceptable it is to find antibiotic resistance and microbiome changes in the throats and guts of men-who-have-sex-with-men (MSM) who use STI prophylaxis. The study will recruit 108 MSM who are using and not using STI prophylaxis. Participants will visit the clinic every 6 months. At each visit, they will provide a throat swab and stool sample, and complete a questionnaire. DNA of the bacteria from the samples will be analysed to identify the bacteria and look for antibiotic resistance.

Post-exposure prophylaxis (PEP) using doxycycline 200 mg within 24 hours of unprotected sexual intercourse to prevent sexually transmitted infections has demonstrated a reduction in the incidence of chlamydial and syphilis infections and syphilis infection by 70% and 73% in men who have sex with men (MSM) undergoing pre-exposure prophylaxis prophylaxis (PrEP) for HIV. Other studies are underway or in development on doxycycline prophylaxis for bacterial STIs, which are particularly common in this population. Monitoring adherence to PEP is of great interest in guaranteeing the effectiveness of this strategy and to be able to assess the uptake of PEP among PrEP users. Among the many methods for assessing adherence, measuring drug concentrations is a more accurate measure of adherence than self-reporting. The therapeutic monitoring of doxycycline and the assessment of adherence have been described using plasma and hair samples, allowing estimation of intake over the last 3-4 days and 4 months, respectively. Nevertheless, these biological matrices present several limitations for application in clinical practice: reflecting the duration of exposure should be more in line with the frequency of visits (2 months), and the collection of hair samples may be difficult due to refusal or short hair. On the other hand, interpretation of the hair assay is limited by the degradation of doxycycline in this matrix, which could lead to underestimation of drug intake. By Therefore, new biological matrices are needed for more accurate assessment of doxycycline adherence in post-exposure prevention monitoring. The objective is to evaluate the pharmacokinetics of doxycycline in plasma, whole blood, dried blood spots (DBS), urine and hair after a single dose of doxycycline in men using oral doxycycline for post-exposure prophylaxis of sexually transmitted infections (syphilis or Chlamydia trachomatis) and having sex with men.