Some 24 million, or 18%, of the 130.5 million prescriptions for antibiotics that ambulatory care providers wrote in 2015 in the United States had no documented reason for using the drug, according to a recent analysis.

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A recent study investigates antibiotic prescriptions for outpatients.

Ambulatory care is a general term for medical care that people who are not staying in a hospital or an institution receive.

It includes, for example, visits to primary care providers — such as doctors’ offices and health centers — as well as visits to gynecologists, dermatologists, urologists, and other specialists.

The new BMJ study also identified another 32 million ambulatory care antibiotic prescriptions as inappropriate. This figure represented 25% of the prescriptions in the dataset.

Combining the figures suggests that up to 43% of such prescriptions in the U.S. are potentially inappropriate, according to the study’s authors.

Such a high level of potentially inappropriate antibiotic prescribing makes it hard to monitor and control the use of these drugs, note the researchers.

The need for strong stewardship is a key strategy in addressing the major public health problem of antibiotic resistance.

“Antibiotic prescribing without making note of the indication in a patient’s medical records might be leading to a significant underestimation of the scope of unnecessary prescribing,” says first and corresponding study author Michael J. Ray, a researcher at Oregon State University (OSU) College of Pharmacy, in Corvallis.

“When there’s no indication documented,” he adds, “it’s reasonable to think that at least some of the time, the prescription was written without an appropriate indication present.”

Ray worked on the study with colleagues from OSU and other research centers in Oregon.

Antibiotic or antimicrobial resistance is the ability of bacteria, fungi, and other germs to survive the drugs that are supposed to kill them. It has become a threat to public health because an increasing number of germs are acquiring this ability.

The discovery of antibiotics was a turning point in human and animal health. Infections that used to maim and kill became treatable. However, a new era has begun, and many people around the world are once again becoming ill and dying from microbial infections.

According to a recent report from the Centers for Disease Control and Prevention (CDC), more than 2.8 million infections every year in the U.S. are antibiotic resistant. In addition, these infections kill more than 35,000 people a year.

The CDC argue that, while dedicated action has helped bring down these figures, the numbers of infections and deaths are still far too high.

One area of concern is the surge of resistant infections in the community. Rising community-based infection increases the number of people at risk and makes it harder to track and contain the spread. The CDC call for “stronger focus and interventions” in this area.

One of the core actions that the CDC recommend is to strengthen stewardship, which includes improving the appropriate use of antimicrobial drugs.

Studies that investigate the appropriate use of antibiotics in the U.S. rely on prescribers documenting the medical reasons for the drugs in patient records. However, there is not always a requirement to do this, which makes it difficult to assess appropriateness of use on a large scale.

Ray and colleagues believe that their study is among the first to investigate the proportion of prescriptions that do not include documented medical reasons, or indications, for prescribing antibiotics.

Their analysis included data from the 2015 National Hospital Ambulatory Medical Care Survey. This gave them access to 28,332 sample visits, representing a nationwide figure of 990.9 million visits in 2015.

The researchers found that around 13% of the visits resulted in an antibiotic prescription, giving a nationwide total of 130.5 million prescriptions.

When they examined the medical reasons for these antibiotic prescriptions, the researchers identified 57% as appropriate, 25% as inappropriate, and 18% as having no documented indication.

“What that means,” says study co-author Jessina McGregor, Ph.D., a researcher in antibiotic stewardship and associate professor at the OSU College of Pharmacy, “is an estimated 24 million antibiotic prescriptions were written without a documented indication, on top of the 32 million that came with a documented but inappropriate indication.”

Adult males were the patients most likely to receive an antibiotic prescription lacking a documented reason, as were patients who spent more than the average amount of time with their doctor, those with long-lasting conditions, and those seeing a specialist.

The antibiotics most likely to be prescribed without documented reasons were those for treating urinary infections and sulfonamides.

In a linked editorial, Prof. Alastair Hay, of the University of Bristol, in the United Kingdom, reflects on the findings.

He says that one reason why doctors might not give a medical indication is that the diagnosis is uncertain.

“Most patients do not present with neatly differentiated symptoms that can be converted into a conclusive diagnosis of infection,” he notes, “so using a definitive diagnostic code would not reflect reality, even when an antibiotic is considered necessary.”

He also suggests that an effective stewardship scheme needs a comprehensive coding system. This should not only require doctors to record a diagnosis for each antibiotic prescription, but also for each infection, whether they prescribed an antibiotic or not.

With a standard measure of illness severity for each diagnosis, such a coding system could go a long way toward helping doctors decide how ill each patient is, in comparison with others.

Together with more precise diagnoses, more vaccination, and better infection control, such knowledge could greatly assist doctors in fine-tuning their prescription decisions.

Sixty percent of antibiotic expenditures originate in ambulatory care settings, and up to 90% of antibiotic use originates there. Clearly, more focus is needed to support well-informed stewardship efforts.”

Michael J. Ray