A recent study by Garbutt and associates evaluated the effect of amoxicillin treatment over symptomatic treatments for adults with clinically diagnosed acute sinusitis.
They performed a randomized, placebo-controlled trial of 166 adults with uncomplicated, acute sinusitis between 2006 and 2009. Patients were randomized to receive a 10 days course of either amoxicillin ( 85 patients) or placebo (81 patients). All received a supply of symptomatic treatments for pain, fever, cough, and nasal congestion to use as needed. On day 3 of treatment, there was no difference in improvement between placebo-takers and those prescribed antibiotics. On day 7, the antibiotic group reported a slight improvement that the researchers said was unlikely to represent a noticeable relief in symptoms, but that edge disappeared by day 10, when 80 percent of patients in both groups reported they felt better or cured.
The main problem in this study is that many of the patients included in it may have not suffered from bacterial sinusitis but a viral one rendering amoxicillin useless. Furthermore, amoxicillin is no longer a reliable antimicrobial for the treatment of bacterial sinusitis. This is because many of the pathogens causing bacterial sinusitis have become resistant to it. These include Streptococcus pneumoniae (5-10% highly resistant), haemophillus influenzae (30-40%), Moraxella catarrhalis (>95%) and Staphylococcus aureus (>80%).
The implementation of the 7-valent pneumococcal conjugate vaccine has created a shift in the isolation rate of pathogens causing sinusitis. The proportion of H. influenzae in relation to S. pneumoniae has increased over the years such that currently they are approximately equal ( about 40%). This shift contributes to the therapeutic inefficacy of amoxicillin.
The reduced efficacy of amoxicillin lead a multidisciplinary expert panel of the Infectious Diseases Society of America to generate new guidelines for the treatment of acute rhinosinusits. These guidelines recommend that amoxicillin-clavulanate is preferred over amoxicillin as empiric antimicrobial therapy in adults and children with acute bacterial rhinosinusitis.