(CNN) Doctors prescribe antibiotics to treat bacterial and fungal infections, but some people in the United States are using antibiotics without a doctor's prescription. That's a public health problem that can increase drug resistance and make it harder to treat infections, according to a study published this week in the medical journal Annals of Internal Medicine.
Researchers gathered data on nonprescription antibiotic use in the United States from 31 studies between 2000 and 2019 and focused on four main populations: patients outside a health care setting, patients in health care settings, Hispanic populations and injection drug users.
Nonprescription antibiotic use included obtaining, storing, taking or intending to take antibiotics without medical guidance. The prevalence of nonprescription antibiotic use varied from 1% (clinic patients) to 66% (Latino migrant workers), while the intention to use nonprescription antibiotics was 25% in the only study that asked. The storage of antibiotics for future use ranged from 14% to 48% across all the groups studied.
"We know that people are using antibiotics that weren't prescribed to them, which isn't safe and isn't good for their health. So in order to tackle the problem we absolutely had to know what was already out there in the literature so we could figure out what the gaps are," said study author Dr. Barbara Trautner, an infectious diseases clinician-investigator at the Baylor College of Medicine and the Houston Veterans Affairs Medical Center, who's affiliated with the Center for Innovations in Quality, Effectiveness and Safety.
One of these gaps was figuring out what factors drove people to self-treat and use nonprescription antibiotics. The studies cited several factors including poor health-care access, long wait times at the doctor's office, costs of antibiotics and doctor visits, lack of transportation and embarrassment about getting treatment for sexually transmitted infections.
People got these nonprescription antibiotics through a wide variety of sources, including leftover prescriptions and local markets that sold antibiotics as over-the-counter medications. Other sources were family and friends, flea markets, pet stores, health food stores and online venues. Most of the antibiotics came from leftover prescriptions or friends and family members.
"The overall picture that's given here is way more detailed than I would have known about, particularly the various sources," said Marc Lipsitch, professor of epidemiology at the Harvard T.H Chan School of Public Health, who was not involved with the study. "To me, what's important about this study is that [nonprescription antibiotic use] is a form of antibiotic use that contributes to the burden of antibiotic resistance."
Antibiotic resistance is when bacteria or fungi develop an ability to outlast drugs designed to kill them, a result of exposure to an antibiotic that's used too much or too often. The antibiotic's effects can wear off over time and lead to persistent infections that require extensive, expensive medications.
In the United States, 2 million people develop antibiotic-resistant infections each year, and 23,000 die from those infections, according to the US Centers for Disease Control and Prevention.
Nonprescription antibiotic use in the United States hasn't been studied extensively, but studies in Europe have shown an association between high nonprescription drug use and high levels of antibiotic resistance, according to Dr. Larissa Grigoryan, lead author of the study and assistant professor in the Department of Family and Community Medicine at the Baylor College of Medicine, who's also affiliated with the Center for Innovations in Quality, Effectiveness and Safety.
Another problem with nonprescription antibiotic use is the risk of side effects. Antibiotics can cause "severe allergic reactions" or "disruption of the microbiome" when normal bacteria in the body are killed off, Grigoryan said. A disrupted microbiome can allow bacteria like Clostridium difficile to grow in areas previously occupied by normal bacteria and can lead to diarrhea and even death.
"People are clearly being driven to take the antibiotics without a prescription because of concerns they have for their own health or their family members health and maybe not knowing that they could be endangering the health they're trying to help," Trautner said. "If we don't correct the rising tide, we're going to be seeing more and more [adverse effects]."
The research had some limitations, including that the 31 studies used different methods of data collection through online surveys, phone calls and social media use. Furthermore, certain population subgroups were studied more than others, including the Hispanic population and injection drug users.
Because of the variety of data sources, "we can't present like one number" that can say how much antibiotic use is from nonprescription use, Grigoryan said.
That's why more research needs to be done to understand the scope of nonprescription antibiotic use before correcting it.
"Antibiotics is one of the few medications where, if you take it, you can hurt other people," Trautner said. "We want to go to people across multiple demographics. ... We need that information before we can design an intervention."