ID Consult

Why 10 days of antibiotics for infections is not magic


 

References

In the United States, we treat almost all infections for 10 days. Why? In France, most infections are treated for 8 days. In the U.K., most infections are treated for 5 days. In many other countries, infections are treated until symptomatic improvement occurs. Can everyone outside the United States be wrong? What is the evidence base for the various recommended durations? Moreover, what is the harm in treating for longer than necessary?

The U.S. tradition of 10 days’ treatment for infections arose from the 1940 trials of injectable penicillin for prevention of acute rheumatic fever in military recruits who had group A streptococcal pharyngitis. Injections of penicillin G mixed in peanut oil produced therapeutic levels of penicillin for about 3 days. Soldiers who received three sequential injections had the lowest occurrence of rheumatic fever; two injections were not as good and four injections did not add to the prevention rate. So three injections meant 9 days’ treatment; 9 days was rounded up to 10 days, and there you have it.

Dr. Michael E. Pichichero

Dr. Michael E. Pichichero

We have come a long way since the 1940s. For strep throat, we now have three approved antibiotics for 5 days’ treatment: cefdinir, cefpodoxime proxetil, and azithromycin, all evidence based and U.S. Food and Drug Administration approved. One large study was done in the 1980s with cefadroxil for 5 days, and that duration was as effective in strep eradication as was 10 days, but the company never pursued the 5-day indication.

The optimal duration of antibiotic treatment is generally considered to be 10 days in the United States, however, there is scant evidence base for that recommendation. The recent American Academy of Pediatrics/American Academy of Family Physicians guidelines endorse 10 days of treatment duration as the standard for most acute otitis media (AOM) (Pediatrics 2013;131[3]:e964-99), but acknowledge that shorter treatment regimens may be as effective. Specifically, the guideline states: “A 7-day course of oral antibiotic appears to be equally effective in children 2- to 5 years of age with mild to moderate AOM. For children 6 years and older with mild to moderate AOM symptoms, a 5- to 7-day course is adequate treatment.” A systematic analysis and a meta-analysis have concluded that 5 days’ duration of antibiotics is as effective as 10 days’ treatment for all children over age 2 years and only marginally inferior to 10 days for children under the age of 2 years old (Cochrane Database Syst Rev. 2010;[9]:CD001095).

Thirty years ago, our group and others began to do studies involving “double tympanocentesis,” where an ear tap was done at time of diagnosis and again 3-5 days later to prove bacterial cure for various antibiotics that were in trials. We learned that if the organism was sensitive to the antibiotic chosen, then it was dead by days 3-5. Most of the failures were due to resistant bacteria. So treating longer was not going to help. It was time to change the antibiotic if clinical improvement had not occurred. Our group published a study 15 years ago of 2,172 children comparing 5-, 7-, and 10-days’ treatment of AOM, and concluded that 5 days’ treatment was equivalent to 7- and 10-days of treatment for all ages unless the child had a perforated tympanic membrane or the child had been treated for AOM within the preceding month since recently treated AOM was associated with more frequent causation of AOM by resistant bacteria and with a continued inflamed middle ear mucosa (Otolaryngol Head Neck Surg. 2001 Apr;124[4]:381-7). Since then we have treated all children with ear infections for 5 days, including amoxicillin and amoxicillin/clavulanate as well as various cephalosporins unless the eardrum had perforated or the child had a recurrent AOM within the prior 30 days. That is a lot of patients in 15 years, and the results have been just as good as when we used 10 days as standard.

Acute sinusitis is another interesting story. The AAP guideline states: “The optimal duration of antimicrobial therapy for patients with acute bacterial sinusitis has not received systematic study. Recommendations based on clinical observation varied widely, from 1- to 28 days (Pediatrics. 2013 Jul;132[1]:e262-80). The prior AAP guideline endorsed “antibiotic therapy be continued for 7 days after the patient becomes free of symptoms and signs (Pediatrics. 2001 Sep;108[3]:798-808). Our group reasoned that the etiology and pathogenesis of sinusitis and AOM are identical, involving ascension of a bacterial inoculum from the nasopharynx via the osteomeatal complex to the sinuses just like ascension of infection via the eustachian tube to the middle ear. Therefore, beginning 25 years ago, we began to treat all children with sinus infections for 5 days, including amoxicillin and amoxicillin/clavulanate, as well as various cephalosporins. Again, that is a lot of patients, and the results have been just as good as when we used 10 days as standard.

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