I'll start with the bottom line first. It is absolutely false that continuing to take antibiotics after you feel completely better will reduce the emergence of antibiotic resistance. Quite to the contrary, it will very likely promote the emergence of antibiotic resistance!
How did we get to this point, with such a huge gulf between reality and dogma? And how could so much of the medical community have been so wrong for so long?
Let's make one thing explicitly clear. Historically, doctors and patients have both been pretty dreadful about using antibiotics appropriately. We've long prescribed antibiotics out of fear and habit, not science.
Indeed, as far back as 1945, Alexander Fleming, the man who discovered penicillin in 1928, warned the public that people were taking penicillin to treat diseases not caused by bacteria, and that this unnecessary use of penicillin was going to breed out antibiotic resistance. He warned that those who so abused penicillin would be "morally responsible" for the deaths that ensued from penicillin-resistant infections.
He was right.
The sad thing is, society never did listen. Recent data confirm that our use of antibiotics has gotten no better in the modern era.
It has been estimated that 30 to 50 percent of antibiotic use in the U.S. is unnecessary. In my opinion, those numbers are rather hilariously low. I would that estimate 75 percent or more of antibiotic use is unnecessary. You see, I, and experts like me, have a more stringent definition of when antibiotic use is appropriate or not, which includes giving too long a course of antibiotics to patients who need them.
The truth is, we do not know how long a course of antibiotics is necessary to treat most types of infections. Even in the modern scientific era, the primary basis for the duration of most courses of antibiotics is a decree Constantine the Great issued in A.D. 321 that the week would consist of seven days. That's why your doctor gives you seven or 14 days' worth of antibiotics!
If good old Constantine had decreed four days in a week, doctors would be prescribing antibiotics in four- or eight-day courses, rather than seven- or 14-day courses. I refer to seven- or 14-day antibiotic courses as "1 or 2 Constantine units" to underscore the absurdity of the basis for these durations.
But in the last two decades, we actually have had dozens of clinical trials published demonstrating that shorter courses of antibiotics are just as effective as longer courses (see table).
Furthermore, the shorter-course regimens led to lower rates of antibiotic resistance.
Enter Dr. Louis Rice, chair of medicine at Brown University. Rice has long been an international leader in antibiotic use and resistance. Ten years ago, he gave a lecture at a national infection meeting in which he challenged physicians to move to evidenced-based, short-course antibiotic regimens.
He then went a step further and became the first expert to publicly challenge the nonsense that continuing to take antibiotics after you feel better would somehow prevent the emergence of resistance.
Rice is the man who first called out that the emperor had no clothes. He traced the origin of this incorrect myth back through time. He discovered that the myth appears to originate due to a general misunderstanding of the findings in an article published in 1945, one of the first descriptions of penicillin therapy for pneumonia (lung infection).
This misunderstanding blossomed into the extremely pervasive, indeed erroneous, silly urban legend that continuing antibiotics beyond resolution of symptoms somehow helps reduce antibiotic resistance.
Not only is there absolutely no evidence that taking antibiotics past when you feel better will reduce antibiotic resistance, it doesn't even make sense. The fact is, the longer you take an antibiotic for, the greater the chance that antibiotic-resistant bacteria will emerge in your body and in the environment around you.
There are some chronic infections, such as tuberculosis, where you do indeed have to take long courses of antibiotics, not to prevent resistance, but rather to cure the infection. But for most acute bacterial infections, short courses of antibiotics result in equivalent cure rates, and with less chance of causing the emergence of antibiotic resistance among the bacteria in and on your body.
The World Health Organization (WHO) agrees that there is scant, if any, evidence for long courses of antibiotics, saying that "shorter treatments make more sense – they are more likely to be completed properly, have fewer side effects and also are likely to be cheaper."