BioEd Online

Cutting the length of time that patients take certain antibiotics could help to tackle the rise in drug resistance. So say the authors of a study showing that just three days' worth of drugs can fight pneumonia just as well as a longer treatment.

Many antibiotics are prescribed for a week, ten days, or more, and patients are usually told to finish the course of pills to ensure that all the infection-causing bugs are eradicated. It is widely thought that not finishing the full course of drugs may allow a few of the hardiest bugs to linger, raising the risk that an antibiotic-resistant population of bacteria can then develop.

But there is no particular reason for the length of some antibiotic treatments, says infectious-disease expert Jan Prins of the Academic Medical Center in Amsterdam, the Netherlands. In general, the drugs are given for five, seven or ten days simply because that's what worked in the initial trials.

Three-day cure

Prins and his colleagues decided to test the conventional wisdom. They studied people admitted to Netherlands hospitals with pneumonia, because respiratory tract infections of this type are one of the most common reasons that antibiotics are prescribed. The standard length of antibiotic treatment for pneumonia is 7-10 days.

The researchers treated each patient with a three-day intravenous course of the antibiotic amoxicillin. Of the 119 who improved, half continued to receive antibiotic pills for another five days, and another half were given a placebo pill.

Four weeks after the start of treatment, nearly 90% of patients in both groups were considered cured of the infection. Three days' worth of drugs was enough to kill most of the bacteria; the other five seemed to be superfluous.

At least for pneumonia, the finding counters the idea that a fleeting dose of antibiotics might allow some resilient bugs to survive and develop antibiotic resistance. "There's no reason to assume you leave semi-resistant bacteria behind," Prins says. Their results are published in the British Medical Journal¹.

Testing time

In fact, the reverse could be true: unnecessarily long drug courses could fuel overuse of antibiotics and actually encourage bacteria in our guts to acquire and spread resistance. The recommended time course for some other antibiotics for ear and urinary tract infections has already been shortened because of similar studies; for some types of throat infection, the use of antibiotics is discouraged altogether because most patients get better on their own.

"There is always the possibility that a lower dose or shorter duration might be equally efficacious," says infectious disease specialist Jim Wilde at the Medical College of Georgia, Augusta.

Medical researchers now have to prove that other antibiotic courses can be shortened, by testing each infection and each antibiotic treatment in similar studies. "You have to find out for each infection which is the best course," Prins says.

Until those results are in, the researchers are keen to emphasize that patients should not stop taking their prescribed antibiotics prematurely. For many infections there is strong evidence that the drugs should be taken for a week or longer.

"You want to treat not too little and not too long," says Wilde. "But in many cases you don't have the exact number."

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