Uncomplicated urinary infections: How do short and long courses of antibiotics compare?

Three days of antibiotics are almost always enough to get over a urinary tract infection. Taking an extra two days of antibiotics can get rid of the last of the bacteria causing the infection, but the price is more adverse effects.

Uncomplicated urinary tract infections (UTIs) are most common among young women. They are caused by bacterial infection. On average, young women will get an infection every one or two years. They will notice some burning pain when they pass urine, and it often means they need to go to the toilet much more often too. The symptoms can be very unpleasant, but the infection will rarely lead to any serious health problem. Some women get so many UTIs that it becomes a serious bother to them.

Antibiotics can clear up UTIs and quickly relieve the symptoms, because they can kill the bacteria. Years ago, there even used to be a single high-dose antibiotic that would do the job. That one-off therapy got rid of the symptoms quickly, but there were often enough bacteria left over for the infection to return. So today UTIs are treated with either a three-day short course or a longer course of antibiotics (five days or more).

To find the answer to the question of how long it might be best to take antibiotics, researchers from the Cochrane Collaboration studied the results of 32 trials that included more than 9,600 women. After their analysis, the researchers came to several conclusions that could help decide how long to take antibiotics.

The first conclusion: three days of treatment is usually enough to relieve symptoms for women with uncomplicated UTI. Taking antibiotics for longer does not improve symptom relief, but it does lead to more adverse effects.

For example, in one trial, 15 out of every 100 women (15%) taking an antibiotic short-term had an adverse effect. But for the women taking the same antibiotic for longer, 20 out of 100 had adverse effects (20%). Mostly these adverse effects were very mild, but they were bothersome enough for some women to stop about 3 women out of 100 taking the antibiotics longer term (3%).

Another difference was found when the urine of the women was tested. When there is a UTI, bacteria can be detected in the urine. After three-day antibiotic treatment, bacteria could still be found in some women's urine. After five days, though, the urine was bacteria-free in almost all the women.

Whether these last few bacteria cause any problem is not really known. The trials could not tell if the remaining bacteria led to the infection coming back. The choice of length of therapy then depends on the individual woman's point of view. Women who want to be as sure as possible that the infection is completely gone, might choose to take the drugs for five or more days. For women who are only concerned about getting over the symptoms, three days might be enough.

© IQWiG (Institute for Quality and Efficiency in Health Care)