Acute sinusitis is a common infection, usually attributed to Streptococcus pneumoniae, Haemophilus influenzae and, less often, Moraxella catarrhalis. As these organisms are generally susceptible to less expensive antibiotics such as amoxicillin and co-trimoxazole (trimethoprim plus sulfamethoxazole), de Ferranti and colleagues questioned the role of the more expensive broad-spectrum antibiotics and conducted a meta-analysis to compare the two types of antibiotics.

The authors searched Medline and other sources for randomized trials of treatment of acute sinusitis or acute exacerbations of chronic sinusitis that compared amoxicillin or a folate inhibitor with another antibiotic. The trials were examined for quality based on randomization, blinding, description of patient follow-up, clinical outcomes and use of decongestants. Of the 80 trials identified, only 27 met the study criteria. Six of these trials were placebo-controlled, 13 compared amoxicillin with other antibiotics and eight compared a folate inhibitor (e.g., co-trimoxazole or trimethoprim plus sulfametopyrazine) with other antibiotics. The trials involved 2,717 patients with a mean age of 25 to 44 years (in all but two trials). The trials differed in the use of decongestants, the diagnostic criteria for sinusitis and the definitions of outcomes.

In studies comparing any antibiotic with placebo, antibiotics reduced the number of treatment failures by almost one half, but symptoms resolved in 69 percent of patients treated with placebo. When amoxicillin was compared with other antibiotics, no significant differences were found in the rate of cure or failure. The authors calculate that treating 100 cases of acute sinusitis with amoxicillin instead of a more expensive antibiotic would lead to less than one additional treatment failure. Similar results were obtained with folate inhibitors, but the conclusions were limited by the relatively small number of cases studied. Because of the wide differences between the studies, no meaningful conclusions can be drawn concerning radiographic and bacteriologic evidence of cure. It was noted that approximately two thirds of cases of acute sinusitis improve spontaneously with no antibiotic therapy.

The authors conclude that traditional antibiotics, such as amoxicillin and folate inhibitors, have similar efficacy to newer medications and could decrease the development of antibiotic resistance in bacteria and reduce the costs of treating this common condition.