Doxycycline: A pill with more than 50 years of history holds great hope for stopping the rise in syphilis and chlamydia | Society

Innovation using cutting-edge treatments is a medical priority to address major health challenges. However, sometimes the solution to some problems can already be found in the medicine cabinet, and scientific advances actually involve exploring new ways to use old molecules. This is called drug repositioning, and at the moment it is the best alternative that researchers have found…

Innovation using cutting-edge treatments is a medical priority to address major health challenges. However, sometimes the solution to some problems can already be found in the medicine cabinet, and scientific advances actually involve exploring new ways to use old molecules. This is called drug repositioning, and for now it is the best alternative that researchers have found in the face of one of the biggest challenges facing international health authorities: a sharp rise in sexually transmitted infections (STIs), a global phenomenon that is punishing Europe with particular brutality.

“Doxycycline is an antibiotic that has been used for decades to treat many infections. A new study finds that a 200-milligram tablet taken as prophylaxis within 72 hours of risky sexual activity reduces the likelihood of contracting syphilis and chlamydia, two of the most common STIs, by about 80%. And this change in the use of the drug is a significant achievement, since for the first time an easy-to-use pharmacological intervention has been described to prevent infections that are so common in some groups,” explains Santiago Moreno, head of the Infectious Diseases Service of the Ramon y Cajal Hospital (Madrid) .

Post-exposure prophylaxis with doxycycline, also known as “doxy-PEP,” has recently become a topic of much interest at scientific conferences on STIs. The reason is the uncontrollable rise in infections, a phenomenon that the World Health Organization (WHO) and the European Center for Disease Control and Prevention (ECDC) have warned about. The incidence of syphilis in the EU, for example, increased by 34% in 2022 compared with the previous year, while in Spain the incidence has increased 10-fold this century – from 1.77 cases per 100,000 inhabitants in 2000 to 17.10 in 2022. – according to a recent report from the Ministry of Health.

Maria del Mar Vera, president of the research group on sexually transmitted infections of the Spanish Society of Infectious Diseases and Clinical Microbiology (GeITS-SEIMC), explains that “this global growth has forced the promotion of new preventive strategies, and doxycycline provides excellent results. very promising.” However, this expert cautions that “the risk of promoting the development of resistance or possible side effects from continued use of this drug” are limitations that require “prudence” before expanding the use of doxy-AEDs.

Last March, three SEIMC research groups – GeITS, GeSIDA and GEMARA, the latter on antimicrobial resistance – published a “position paper” approved by the Ministry of Health, which compiled the available scientific evidence and included some recommendations. According to the text, “Doxy-PEP will be assessed only and on an individual basis for MSM (men who have relationships with men) or MTG (transgender women) who have sex with men and have had a recurrent STI in the past year. “The pill “should be taken as soon as possible after risky” sexual intercourse, “ideally within the first 24 hours and never after 72 hours,” the document continues.

The SEIMC groups also insist that “STI prevention with Doxy-PEP should not come at the expense of established preventative measures, so it is critical to educate the patient about the importance and necessity of engaging in protected sex.” .

French researchers in 2018 published the first large study on doxycycline as post-exposure prophylaxis to prevent STIs. The study followed 232 participants—men who have sex with men and transgender women—using PrEP, another pill that prevents the spread of HIV when taken before risky sex, for 10 months. The drug has shown greater effectiveness in preventing viral infections, but that success has had the unwanted effect of reducing condom use among some groups, which in turn has contributed to increases in other STIs, according to experts surveyed.

“Studies in France and the US have shown that Doxy-AED reduces the risk of syphilis and chlamydia by 80% or more among PrEP users and patients with HIV compared with placebo. On the other hand, against gonorrhea, doxycycline did not show significant effectiveness, which is undoubtedly due to the resistance that the gonococcus (the bacterium that causes it) has already developed, explains Moreno. Another study conducted among women in Kenya found no significant decline in this group.

These findings have opened a debate about the scope of use of Doxy-PEP as a public health strategy. Three SEIMC groups advocate its use on an individual basis only if there is a history of recurrent STIs. “Despite promising results in men who have sex with men (MSM) and transgender women (TGW), there are still many unknowns regarding the impact on effects at both the individual level (adverse effects or microbiome changes) and individual level . at the population level (selection and spread of antimicrobial resistance),” the document says.

However, some experts believe that given the available data, a further step should be taken. “In recent years we have seen a change in sexual relationships and dynamics, which are now more open and free. This is a positive development, but it has had an unforeseen effect that we need to pay attention to: an increase in the incidence of STIs. The question is how we do it. Evidence has long shown us that using condoms as the only strategy does not work. The advantage of doxy-PEP is so great that we cannot stop implementing it,” defends Jorge García, a doctor at the STI department of the Drassan-Val d’Hebron Center in Barcelona, ​​one of the reference centers in Catalonia.

This position, shared by Moreno, does not deny the risk of developing resistance, but rather considers it a “hypothesis” that needs to be monitored. “The current results do not show an increase in resistance, so this does not seem to be a sufficient reason to limit access to doxy-AEDs,” Garcia insists.

This debate—or failure to determine which recommendations should be adopted—is repeated internationally. “There are some inequalities, but the vast majority of international agencies or scientific societies with the most influence advocate not going beyond the use of Doxy-PEP in patients with recurrent STIs and medical evaluation on a case-by-case basis. And this is what the paper from the three SEIMC research groups advocates,” says Maria del Mar Vera.

Julia del Amo Valero, director of the Department of Health’s HIV, STI, Viral Hepatitis and Tuberculosis Control Unit, stresses that her agency is “working closely with the ECDC, analyzing scientific evidence to agree on a common position on the possible widespread use of post-exposure prophylaxis with doxycycline in the prevention of syphilis and chlamydia . Following this line, the ministry collaborated and reviewed the SEIMC document, which was “disseminated to communities under the National Antimicrobial Resistance Plan (PRAN) to collaborate on this new prevention strategy and its possible implications,” he added.

Doxycycline is a so-called tetracycline antimicrobial and has been on the market since the late 1960s. “They were one of the first groups of antibiotics to be discovered and have been used for more than half a century, so we know them well. They are indicated for the treatment of multiple infections, including some STIs, as well as respiratory infections, skin infections…,” explains Pablo Caballero from the scientific dissemination department of the General Council of Official Colleges of Pharmacists.

There are fifteen drugs on the market with this molecule, although almost all contain 100 milligrams, and only one—Proderma 200 mg, most commonly used for skin infections—is currently dose-adapted to Doxy-PEP. Doxycycline, despite being considered a drug without too many side effects, is clearly contraindicated “during pregnancy because it affects fetal bone formation,” Caballero says. For this reason, the drug should also not be used in children under eight years of age, in whom it may also cause permanent stains on the teeth, a side effect that affects some people born in the 1960s and 1970s who received this antibiotic as children. .