Measuring antibiotic levels in otitis media

Antibiotic concentrations in serum and middle ear effusion (MEE) are important in determining treatment success in acute otitis media, but studies to measure concentration levels are often performed in chronically infected patients where there is little inflammation. In this open, single-center study, 26 patients with acute otitis media were enrolled to assess antibiotic penetration in inflamed ears. Of the 26 patients, 4 were non-evaluable, 6 formed a control group and the others were randomized into three groups. Each of the three groups was given a single oral dose of cefuroxime axetil suspension, 15 mg/kg. Food was administered approximately 20 minutes before the drug in order to maximize drug absorption. Cefuroxime concentrations in serum and MEE were assessed at 2-3 (group 1), 3-4 (group 2) and 4-5 (group 3) hours following dosing. Sampling of MEE was performed with tympanocentesis under local anesthesia and the drug was assayed by HPLC-mass spectrometry. The serum concentrations of cefuroxime were found to be above the minimal inhibitory concentration (MIC) for penicillin-sensitive Streptococcus pneumoniae for 100% of the dosing interval and 42% of the time for intermediate-resistant strains. For both Haemophilus influenzae and Moraxella catarrhalis, serum cefuroxime levels were above the MIC for 42% of the time between doses. This study indicates that cefuroxime axetil penetrates the inflamed middle ear effectively in acute otitis media after oral dosing. Serum levels were maintained above the MICs of important bacterial pathogens in otitis media for more than 5 hours after dosing, which is equivalent to 42% of the dosing interval. Thus, the important statistic of 40-50% of time above MIC, required for beta-lactam antibiotics to produce the maximal bacteriological cure rate of 80-85%, is achieved.