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Cefaclor given per os 20 mg/kg body weight was readily absorbed and distributed to adenoid tissue and to middle ear effusion in children with chronic OME. The levels obtained were above the MIC values of most strains of respiratory pathogens. The penetration characteristics were the same after the first and the 20th dose in a b.i.d. regimen. Elimination was completed within about 12 h. The double dose, 40 mg/kg body weight, did not give higher levels but a longer duration.

Seventy-nine patients that had persistent or recurrent secretory otitis media for over 3 months and were scheduled for myringotomy and/or adenoidectomy received a single dose of cefaclor (20 or 40 mg/kg) orally 0.5-4 hours before surgery. Cefaclor concentrations were determined in serum, middle ear fluid and/or blood-free adenoid tissue homogenate using microbiological methods. Concentrations in adenoid homogenate ran parallel to those in serum, indicating a rapid penetration to adenoid tissue. Penetration to middle ear fluid was delayed in comparison. In the 51 patients receiving 20 mg/kg, peak levels occurred after 0.5 hour in serum as well as in adenoid homogenate and middle ear fluid with mean values of 29, 7.5 and 5.1 mg/l, respectively. Concentrations in the middle ear fluid were greater than 2.0 mg/l from 0.5 to 3 hours after this dose. In the 28 patients receiving 40 mg/kg, concentrations levelled after 0.5 hour in serum and in adenoid homogenate, with mean values of 21-33 mg/l and 6.3-12 mg/l, respectively. Concentrations in the middle ear fluid reached 7.8 mg/l 2 hours after this dose. A dose of 20 mg/kg appears to be suitable for treatment of respiratory tract infections on a b.i.d. basis.

Penetration into the middle ear of four antibiotics commonly used in treatment of otitis media was studied by administering a single oral dose of amoxicillin, cefaclor, erythromycin-sulfisoxazole, or trimethoprim-sulfamethoxazole to 83 children with chronic serous otitis media. The antibiotic was given 15-240 min before the removal of middle ear fluid (MEF) by ventilation tubes inserted through the tympanic membrane. At the time MEF was obtained, a sample of blood was drawn from the patient, and concentrations of antibiotic in both specimens were assayed either microbiologically by a disk diffusion method or by high-pressure liquid chromatography. Amoxicillin had the highest ratio of mean peak concentration in MEF to minimal inhibitory concentration (MIC) for the three most common pathogens of otitis media (Streptococcus pneumoniae, ampicillin-sensitive Haemophilus influenzae, and Streptococcus pyogenes), whereas trimethoprim-sulfamethoxazole had the highest ratio of mean peak concentration in MEF to MIC for ampicillin-resistant Haemophilus influenzae.

Fifty children aged 1 to 13 years with chronic or recurrent otitis media with effusion received a single dose of cefaclor (15 mg/kg body weight) by the oral route 30 minutes to seven hours before the removal of middle ear effusion and insertion of tympanostomy tubes. Serum and middle ear aspirate concentrations of the antibiotic were determined employing a microbiological assay technique by a disk diffusion method. Middle ear specimens were also cultured for aerobic bacteria. The mean peak serum concentration level (8.49 +/- 7.89 micrograms/ml) was observed after 30 minutes, whereas the middle ear peak level (0.47 +/- 0.78 micrograms/ml) occurred after one hour. Of the 87 middle ear specimens, 37 had cefaclor concentrations which were detectable within the resolution of the bioassay method (greater than 0.16 micrograms/ml). There was no correlation between the type of middle ear effusion (mucoid or serous) and the concentration of cefaclor in the middle ear. Only 18% of the middle ear cultures were positive for aerobic bacteria; Hemophilus influenzae was the most common organism.