A pill to be taken within hours of unsafe sexual intercourse greatly reduces the chance of developing sexually transmitted infections: it’s called doxyPEP and works a bit like the “morning after pill”, only instead of avoiding pregnancy it prevents diseases like syphilis and chlamydia.
In the USA it is under discussion a lot because, after years of good results in trials, it could become a widely used and easily obtainable drug, were it not for a not negligible global risk: in an attempt to stem sexual infections, doxyPEP, which is an antibiotic, could promote the spread of drug-resistant superbugs.
A known antibiotic. The pill is based on doxycycline, an antibiotic widely used to treat various bacterial infections (in addition to chlamydia, syphilis and gonorrhea also acne, otolaryngological, gastrointestinal or urinary tract infections) already available by prescription. The novelty would be its PEP form (which stands for post-exposure prophylaxis) in combination with sexually transmitted infections (STIs). The idea is that by taking a single dose of doxycycline after unprotected intercourse, the antibiotic can kill any sexually transmitted bacteria before it can trigger an actual infection.
Moreover, doxycycline is already officially used in PEP form for other diseases: the US Centers for Disease Control recommend a dose after tick bites to prevent Lyme disease or after having been in contact with water contaminated by the leptospirosis bacterium, a dangerous zoonosis that can be transmitted to humans.
Green light for everyone? In the US, a decision is being made whether to introduce it by law also to prevent sexually transmitted diseases. Currently only a small number of US doctors prescribe it for this purpose and only to a few patients affected by recurrent infections (for example because of HIV). As explained on Vox, as a drug approved by the Food and Drug Administration, the antibiotic can also be prescribed for “off label” uses, ie different from the original ones for which it was approved. But if instead it were decided to recommend it to reduce the incidence of sexually transmitted infections, then it would become much more widespread.
Promising studies. The data supporting this use of doxycycline comes from two human clinical trials, one conducted in France and published in 2017 and one in Seattle and San Francisco soon to be published, the results of which were anticipated at a congress on HIV quest ‘year.
Both studies were conducted on men who have sex with other men, a population considered to be more at risk for sexually transmitted infections; both involved HIV-infected patients, although the American study also included non-HIV-positive people.
In both studies, subjects were divided into two groups, only one of whom was able to take doxyPEP within 24 hours of each unprotected intercourse. Volunteers were able to access condoms and advice on the prevention of venereal diseases and HIV, in order to reduce the health risks associated with sex in general. In both studies, doxyPEP was very effective in preventing syphilis and chlamydia (halved in the French trial and dropped by two-thirds in the US). The drug has been less powerful against gonorrhea, especially in France, but it has long been known that this infection is developing resistance against various types of antibiotics. Another trial, this time on women, is underway in Kenya.
From the frying pan to the grill? Even if doxyPEP is not a perfect drug (it has non-negligible side effects, for example on the digestive system) it would be of great help in reducing the incidence, complications and costs of sexually transmitted infections, which are booming especially in the USA. On the other hand, making an antibiotic widely available to be taken in advance is the perfect recipe for selecting antibiotic-resistant superbugs.
According to some studies on a small number of patients, doxycycline is already giving rise to phenomena of this type, at least on an individual level. Those who take it for a long time, to treat chronic conditions, develop more resistant bacteria in the mouth and intestines, as well as “tougher” versions of the bacterium Staphylococcus aureus in the nose. None of these studies have clarified what this would entail in the long run, if those bacteria were able to spread outside.
Let’s think about it. We need doxycycline: the antibiotic is used to treat pneumonia and other serious infections especially in developing countries, and if it becomes unusable because it is now “fresh water” for bacteria, we would lose an important public health tool. If doxyPREP were prescribed to avoid sexually transmitted infections, its consumption would increase 800 times compared to current use, and this could promote antibiotic resistance phenomena around the world. The data to prove it are not yet there – we should live in the future! – but the risk exists, and it cannot be ignored.