Local concentration of systemic amoxicillin and metronidazole in healthy and inflamed gingiva: a comparative in vivo study

Background One of the most recommended methods of systemic antibiotic administration in periodontics is the combination of amoxicillin and metronidazole, which has great inhibitory effect on periodontal pathogens. The aim of this study is to determine the local concentrations of these drugs in gingiva and compare its distribution in healthy and inflamed tissues. Methods The study population was selected from patients referred to our department. Fifteen subjects were referred for crown lengthening, and another 15 subjects required flap surgery because of severe periodontitis. All 30 patients received three doses of amoxicillin 500 mg plus metronidazole 250 mg before surgery. Tissue samples were gathered during surgery, and chemotherapy was continued for 7 days with 8-h intervals. After 7 days, during the second appointment, the next samples were collected. Samples were sent to the laboratory to determine the drug concentration with the use of high-performance liquid chromatography. Results Amoxicillin concentration in healthy gingival tissue was not detectable. The concentrations after 24 h and 7 days of administration were 25.9±4.1 and 124.8±18 μg/mL, respectively. The values for metronidazole were 28.86±1.7, 1.70±0.3, and 36.0±1.5 μg/mL. Conclusions The combination of systemic amoxicillin and metronidazole for 7 days has sufficient gingival connective tissue concentration much more than the minimum inhibitory concentration in healthy and inflamed tissue.