Nearly half of Canadian seniors who go to a family doctor about a cold or other non-bacterial respiratory infection leave with a prescription for an unnecessary antibiotic, say researchers who aim to prevent the public health harm caused by such overuse.

Antibiotics do not work against the viruses that cause upper respiratory tract infections such as the common cold and acute bronchitis.

Overuse of antibiotics is a major public health concern, which the United Nations pegs as important in scale as HIV and Ebola.  

The overuse of antibiotics for respiratory infections threatens a vital tool physicians rely on to treat severe bloodstream infections, say doctors and researchers at the Institute for Clinical Evaluative Sciences in Toronto and Western University in London, Ont.

In Monday's online issue of the Annals of Internal Medicine, researchers looked at antibiotic prescribing among 185,014 people aged 66 or older who went to a primary care physician in 2012 in Ontario. 

Dr. Michael Silverman

Dr. Michael Silverman says doctors tend to prescribe more antibiotics later in the day, when they are tired of saying no to patients. (Western University)

"Almost half of people where the doctor felt that this was probably nonbacterial still got an antibiotic anyway," said Dr. Michael Silverman, author of the study and chair of infectious diseases at Western.

"We think that this is occurring out across Canada and it's occurring in the United States," he said.

The investigators expect that their findings on antibiotic prescribing would also apply in other age groups. They focused on seniors because they had access to data on nearly all prescriptions for those aged 66 and older. 

Patients with possible bacterial infection were excluded from the analysis, as were those with cancer, patients who were immunocompromised or living in a long-term care facility.

Silverman was spurred to study overuse of broad-spectrum antibiotics partly because it's associated with potentially severe side-effects such as diarrhea from C. difficile, a huge issue in Canada and around the world, he said.

"We also now realize these drugs can lead to irregular heartbeats and sudden death. Some of them can lead to tendon rupture. Some of them can lead to drug interactions and have people end up in the emergency room."

The most common infections flagged for unnecessary antibiotic use were:

  • Common cold (53 per cent).
  • Acute bronchitis (31 per cent).
  • Acute sinusitis (14 per cent).
  • Acute laryngitis (two per cent).

The researchers don't want to single out physicians for blame, but said they wanted to see what characteristics helped to predict antibiotic prescribing for nonbacterial infections, in order to target education and prevent the problem.

Time pressures on doctors

For instance, the researchers found antibiotic prescribing tended to be more common among family physicians hurrying to see many patients.

When doctors are surveyed about why they write antibiotic prescriptions for nonbacterial infections, they often say it's because of time pressures to see more and more patients. 

Silverman said this isn't the first example of a financial penalty faced by physicians who take the time to counsel patients.

But steps can be taken to encourage doctors to spend the time. For example, when health officials put a priority on encouraging patients to quit smoking, a billing code specifically for counselling time was introduced, Silverman said.

Decision fatigue

But it's also possible that "decision fatigue" sets in for physicians who have to say no all day to patients asking for antibiotic prescriptions. Silverman said U.S. research suggests doctors tend to prescribe more antibiotics later in the day.

The majority of prescriptions in the new study, 70 per cent, were for broad-spectrum antibiotics that are associated with harms to patients and antibiotic resistance, the researchers found. The other 30 per cent were for narrower penicillin-type antibiotics.

Search for rapid test

The high rate of broad-spectrum antibiotic prescribing in this low-risk group with nonbacterial respiratory infections "is strongly suggestive of inappropriate prescribing," the study's authors wrote.  

One limitation of the study is that the researchers lacked detailed data on the patients' clinical picture or the doctors' motivation to prescribe antibiotics. 

In 2007 in Quebec, Dr. Genevieve Cadieux and Robyn Tamblyn, a professor in the department of medicine and the department of epidemiology and biostatistics at McGill University, also looked at predictors of inappropriate prescribing by primary care physicians. 

Tamblyn said she sees why physicians can be cautious at times when faced with a patient with an infection of unknown source. "With older folks, age-related changes in their immune system and co-morbidities make them more vulnerable."

One of the biggest challenges continues to be distinguishing between viral and bacterial infections,Tamblyn said. That's why the European Union has created a €1 million prize to be awarded to the person or team that develops a rapid test to tell whether a patient needs to be treated with antibiotics. 

"Imagine that something like this will be created, made available through pharmacies, and people could check themselves, just like we all do now for pregnancy," Tamblyn said.