Metronidazole, tinidazole, ornidazole and anaerobic infections of the middle ear, maxillary sinus and central nervous system.

Anaerobic bacteria were isolated from 31% of ears with chronic otitis media and from 28% (or 48% if microaerophilic streptococci were included) of chronic maxillary sinusitis cases. The infections which are the main sources of anaerobic central nervous system infections are typically caused by Bacteroides species and microaerophilic streptococci, respectively. Metronidazole, tinidazole and ornidazole were bactericidal against B. fragilis in vitro, and serum concentrations 50 times the MBC were achieved one hour after oral administration. The concentrations of metronidazole in the middle ear discharge and mucosa of chronic otitis media were 70% of the serum levels. The concentrations of metronidazole, tinidazole and ornidazole in the cerebrospinal fluid of rabbits were 90% of the serum levels. The concentrations of metronidazole and tinidazole in the cerebrospinal fluid of humans were 42% and 80%, respectively, of the serum levels. A review of studies involving the treatment of meningitis and brain abscess cases with metronidazole reveals that, as predicted from the bacteriological findings and tissue distribution investigations, administration of metronidazole has met with much clinical success.