[Pharmacokinetic study of antibiotics in otitis]

Antibiotic concentrations in middle ear fluid can be determined in the purulent effusions of acute otitis media or in chronic effusions at the time of myringotomy with tympanostomy tube insertion. Measurements are usually made using microbiological methods. The concentration of betalactamines in middle ear fluid is 20 to 40% serum concentrations. Therefore, in the treatment of otitis media, it is necessary to use high doses of antibiotics, so that the concentration in the middle ear fluid is higher than the minimum inhibitory concentration (MIC) for the most frequent infecting organisms. Sulfamides penetrate well into the middle ear. On the other hand, the concentration of macrolides is not significant until two or three doses have been delivered and a steady state is reached. While direct measurements of the antibiotic concentrations in middle ear fluid can provide information concerning the effectiveness of the antibiotic relative to the MIC, they do not replace clinical trials in confirming the indications of new antibiotic molecules in the treatment of otitis media. In addition, direct measurements are delicate and show great interindividual variations.