One of the Big Mysteries Solved: How to Correctly Prescribe the Duration of Antibiotic Treatments

Just this week the World Health Organisation WHO has issued a warning that resistance of organisms to antibiotics will become one of the biggest challenges of the upcoming decade. Indeed, the correct prescription of antibiotics is crucial for successful treatment and the WHO states that completing the full length of the treatment is just as important.

But what is actually the correct length of treatment for all the different antibiotics and diseases? How many ward rounds on ICU's have I spent with microbiologists (the maybe most important specialists on our sides!) wondering on how they always had a straight answer on the correct length of treatment. 7 days, 10 days or sometimes 21 days... a little mystery to most intensivists, until now!

Hitchhiking though the the wide space of the internet I finally found secret to this question. Back in the year 2010 Paul E. Sax, a Professor of Medicine at Harvard Medical School him self, posted an excellent blog for the NEJM Journal Watch website. Inspired by a New York Time article by Harvard Professor Daniel Gilbert he finally gave insight into one of the great mysteries of medicine:

To figure out how long antibiotics need to be given, use the following rules:

1. Choose a multiple of 5 (fingers of the hand) or 7 (days of the week).
2. Is it an outpatient problem that is relatively mild?  If so, choose something less than 10 days.  After application of our multiples rule, this should be 5 or 7 days.
3. Is it really mild, so much so that antibiotics probably aren’t needed at all but clinician or patient are insistent?  Break the 5/7 rule and go with 3 days.  Ditto uncomplicated cystitis in young women.
4. Is it a serious problem that occurs in the hospital or could end up leading to hospitalization?  With the exception of community-acquired pneumonia (5 or 7 days), 10 days is the minimum.
5. Patient not doing better at the end of some course of therapy?  Extend treatment, again using a multiple of 5 or 7 days.
6. Does the infection involve a bone or a heart valve?  Four weeks (28 days) at least, often 6 weeks (42 days).  Note that 5 weeks (35 days) is not an option — here the 5′s and 7′s cancel each other out, and chaos ensues.
7. The following lengths of therapy are inherently weird, and should generally be avoided:  2, 4, 6, 8, 9, 11, 12, 13 days.  Also, 3.14159265 days.

In this highly data-driven exercise, it is imporant also to note the number of rules — seven, as in days of the week.

That did not occur by chance

Wow, not much more I can add!


Paul E. Sax, NEJM Journal Watch HIV/AIDS Clinical Care, October 22nd 2010

NYT article by Daniel Gilbert from October 2010

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