Clinical Study to Investigate the Effect of Doxycycline, Pentoxifylline, and Nitazoxanide in Sexually Active Men

Doxycycline is a moderate-spectrum, second-generation tetracycline that is generally well tolerated. It is rapidly and almost completely absorbed after oral administration. First introduced commercially in the 1960s, doxycycline has been used by millions to manage acne and as primary prophylaxis for scrub typhus, leptospirosis, malaria, and Lyme disease. There are anecdotal reports of doxycycline used for syphilis prophylaxis among US and Australian military personnel during the Vietnam War. Doxycycline is a first-line agent for treatment of chlamydia and an alternative regimen for syphilis.An open-label extension of the French national HIV research agency (France Recherche Nord & sud Sida-hiv hépatites [ANRS]) Intervention Préventive de l'Exposition aux Risques avec et pour les Gays (IPERGAY) HIV-prevention study continued participant access to HIV PrEP and examined doxycycline postexposure prophylaxis (Doxy PEP) in MSM and transgender women without HIV [17]. Participants (n = 232) were randomly assigned 1:1 to the intervention-doxycycline 200 mg within 24-72 hours of condomless sexual encounters up to 3 times per week-or to no prophylaxis. Those taking Doxy PEP had lower STI incidence (hazard ratio, 0.57; P = .014). Chlamydia trachomatis and syphilis diagnoses were significantly lower in the intervention arm, with a relative reduction of 70-73% in the intention-to-treat analysis.