“Finish the entire course of antibiotics you were prescribed, even if you feel better.” You may have been told this by your doctor or have this saying deeply ingrained in your mind from infections past. You may also have been told that if you don’t finish your full course of antibiotics, your infection could come back and possibly develop antibiotic resistance.
So what’s the data behind these claims? A paper published in BMJ discusses how this claim came to be and whether it holds up to scientific data.
TL;DR: there’s no evidence that stopping antibiotics early leads to antibiotic resistance. What’s more, taking antibiotics for longer than necessary could actually lead to the development of antibiotic resistance. However, the length of antibiotic treatment needed is hard to define.
The Origins of the Antibiotic Course
In 1941, 13 years after the discovery of penicillin, Howard Florey, a pharmacologist and pathologist, and Ernst Boris Chain, a biochemist, treated the first patient with penicillin. This patient had sepsis due to a Staphylococcus infection and was treated over four days using all of the penicillin they could obtain (less than one day’s worth compared to modern dosage).
While they saw improvements during the treatment process, the patient eventually succumbed to the infection after they ran out of penicillin. However, there’s no evidence that the recurrence of the infection was because of newly created resistance during treatment. Regardless, this trial planted the idea that longer treatment periods could avoid treatment failure.
How Could Antibiotic Resistance Arise During Treatment?
Fleming also found that antibiotic sensitive bacteria could be “acclimatized” to penicillin in the lab and develop resistance when the dose used is too low. A more recent example from the Kishony Lab at Harvard Medical School shows exactly this – antibiotic sensitive bacteria evolving to be highly resistant – on a giant two feet by four feet Petri dish. This bacterial population originally sensitive to antibiotics was exposed to increasing concentrations of antibiotics and at the end was able to grow in antibiotic concentrations 1,000 times as much as the original population could survive.
So how does antibiotics use lead to resistance? In the initial infection, a small population of bacteria grow, picking up mutations spontaneously during replication. Any mutations that are beneficial and help the bacteria survive in the presence of the antibiotic would be selected for during treatment. The gradual increase in antibiotic concentrations makes these smaller evolutionary steps possible.
Little Evidence That Recommended Antibiotic Courses are The Minimum Required Treatment Time In Some Infections
The dosage recommendations for an antibiotic course are driven by the fear of undertreatment, like what Fleming saw in his studies with penicillin, and without concern for overuse.
Now, some recommended treatment times may be able to decrease based on similar outcomes from treatment with shorter courses. A study published in 2012 found that a 3-6 day treatment for Streptococcal pharyngitis throat infections in children was just as effective as the standard 10 day treatment with penicillin. Another study found that a 7-8 day treatment for nosocomial pneumonia had similar outcomes when compared to the standard 10-15 day course in critical patients based on ICU mortality and infection recurrence. This lower dose also led to a lower risk of resistant infections based on previous exposure.
However, shortened antibiotic courses aren’t effective in all cases. In 2016, scientists compared the standard 10 day treatment for otitis media with a 5 day treatment course, but saw more treatment failure for those with only a 5 day course.
Determining what the appropriate treatment length for a bacterial infection is tricky and nearly needs to be done on a personalized level – what’s the infecting organism, where is the infection, etc.
What’s Next For The Antibiotic Course?
These studies show that in some cases, stopping antibiotics earlier has no impact on patient outcome and reduces risk of antibiotic resistance. But determining when to stop antibiotics is tricky. Some hospitals review daily on an individual basis the need for continued antibiotics. However, for primary care patients, most prescriptions are sent off with patients to “complete the course” with no ongoing evaluation of whether it is needed.
As antibiotics are a finite resource that should be conserved, it’s important for broader antibiotics education that antibiotic resistance arises primarily due to overuse, not stopping a course of antibiotics early. Eventually, better point-of-care tests that allow clinicians to identify the cause of infection during a primary care appointment would help practitioners avoid prescribing antibiotics before the cause of illness is known.
Further reading
The Antibiotic Course Has Had Its Day. BMJ. 2017. – This is the original article described in this blog post. Unfortunately this article is behind a paywall on BMJ’s site. But, I was able to find a copy of it on ResearchGate.
Should you finish the course of antibiotics? Yes—(until further notice). Center For Disease Dynamics, Economics & Policy. 2017. – In this piece, Sumanth Gandra, MD, MPH, associate professor of medicine at Washington University School of Medicine in St. Louis, reflects on the statements from the BMJ paper indicating the need for more systematic review of treatment lengths for common infections in clinical trials. Gandra also describes the confusing messages from the media as an outcome of this paper.
Antibiotic duration is a Goldilocks problem. ACP Internist Blog. 2017. – Robert Centor, MD, FACP, a general internist at the University of Alabama School of Medicine, posits that antibiotic treatment length is a “Goldilocks problem” where antibiotic treatment time should be not too long but not too short. Like Gandra, Centor also states that we need more duration studies to determine optimal treatment length.
Medical disclaimer: This website does not provide medical advice. It is intended for informational purposes only. No material on this site is intended to be a substitute for professional medical advice, diagnosis, or treatment.
