The effects of metronidazole administration on clinical and microbiologic parameters of periodontal disease.

The purpose of this study was to assay the concentration of metronidazole in gingival fluid, to correlate clinical and microbiologic parameters of periodontal disease to each other and to the gingival fluid concentration of the drug. Ten subjects with a minimum of two contralateral pairs of periodontal pockets of greater than or equal to 5 mm were utilized. One side of the mouth was selected to serve as the root-planed site while the other was left untreated. On day 0, plaque and bleeding-time indexes and probing depths were recorded. Subgingival plaque was analyzed using phase contrast microscopy. When root planing was completed, the subjects were prescribed either metronidazole or placebo three times daily for seven days. Within 24 hours of the last dose, and thereafter at intervals of 1, 2 and 3 weeks, fluid samples were assayed for metronidazole. Clinical and bacterial data were likewise recorded. The results indicate that root planing with metronidazole appears to be more effective in promoting periodontal health than root planing alone. Concentrations of metronidazole ranging from 5 to 20 micrograms/ml were detectable in fluid samples obtained within 24 hours of administration of the last dose. No discernible levels could be found in samples taken at the longer intervals.