Use of metronidazole as part of an empirical antibiotic regimen after incision and drainage of infections of the odontogenic spaces

The combination of amoxicillin/clavulanate and metronidazole is a widely-accepted empirical regimen for infections of the odontogenic spaces. Once adequate drainage has been established micro-organisms are less likely to grow and multiply, particularly anaerobes. This may obviate the need for anaerobic coverage after drainage in healthy hosts. We studied 60 patients in this randomised prospective study, the objective of which was to evaluate metronidazole as part of an empirical antibiotic regimen after drainage of infections of the odontogenic spaces. Samples of pus were sent for culture and testing for sensitivity. Amoxicillin/clavulanate and metronidazole were given to all patients. After incision and drainage the patients were randomly allocated to two groups. In the first group both antibiotics were continued, and in the second metronidazole was withdrawn. The groups were compared both clinically and microbiologically. There were no significant differences between the groups in the resolution of infection. Thirteen patients (n = 6 in the 2-antimicrobial group, and n = 7 in the amoxicillin/clavulanate group) showed no improvement during the 48 h postoperatively. Overall there was need to substitute another antibiotic for amoxicillin/clavulanate in only 6 cases. Six patients in the amoxicillin/clavulanate group required the addition of metronidazole after drainage. We conclude that in healthy subjects metronidazole is not necessary in the period after drainage, but its prescription should be based on assessment of clinical and laboratory markers of infection.