Cerebrospinal fluid concentrations of metronidazole, tinidazole and ornidazole in rabbits.

The penetration of metronidazole, tinidazole and ornidazole into the cerebrospinal fluid (CSF) of rabbits was determined using a bioassay based on the antibacterial activity of the drugs. After an intravenous dose of 50 mg, the CSF levels of each drug exceeded previously reported minimum bactericidal concentrations against Bacteriodes fragilis. Low serum levels of each drug, produced by intramuscular administration of low doses, resulted in CSF/serum ratios ranging from 0.63--0.73.