Access of metronidazole into the chronically inflamed middle ear with reference to anaerobic bacterial infections.

Strictly anaerobic bacteria were found in about one third of 138 consecutive cases of active chronic otitis media. These infections were always mixed involving aerobes as well. In 79 cases only aerobes were found and 16 cultures were sterile. To provide a basis for possible clinical trials, the penetration of metronidazole into the ear was studied after an oral dose of 2.4 g to patients with chronic otitis media. Significant amounts of biologically active metronidazole were found in 8 of 12 middle ear discharges at 2--4 h, the concentrations varying between 9.4 and 65.0 microgram/ml. Between 2 and 13 h after administration, significant drug concentrations all exceeding the highest reported bactericidal ones were found in the middle ear mucosa in 6 cases of the 8 in which the determinations were possible. Neither the mucosal nor the discharge concentrations correlated with the simultaneous serum levels of metronidazole, which were high in all 23 patients studied.