Concentration of 3 tetracyclines in plasma, gingival crevice fluid and saliva

Background: Systemically-administered tetracyclines have been used widely f or treatment of periodontal diseases with little understanding of their del ivery characteristics to periodontal tissues. This study was designed to me asure concentrations of 3 tetracyclines in gingival crevice fluid (GCF), pl asma and saliva of following systemic administration. Method: The concentration of tetracycline (TC), minocycline (MN) and doxycy cline (DX) was measured in gingival crevice fluid (GCF), plasma and saliva of 20 subjects following single sequential standard oral systemic doses. Gi ngival crevice fluid concentration was measured at 4 sites (2 shallow and 2 deep) before administration, and at 1 h and 2 h following administration. Plasma and saliva concentrations were measured from in samples at the same time points. No antibacterial activity was detected before administration. The highest concentrations were measured 2 h after administration. Results: The average concentrations at 2 h were highest in plasma (TC=1.02, MN=2.18, DX=2.35 mu g/ml). Intermediate concentrations were measured in GC F (TC=0.61, MN=1.49, DX=1.65 mu g/ml). Saliva concentrations (TC=0.09 MN=0. 31, DX=0.47 mu g/ml) were the lowest of the 3 fluids monitored. Data are pr esented indicating that the average GCF concentration of systemically admin istered terracyclines is less than the that of plasma concentration. The co ncentration of tetracyclines in GCF was strongly associated with plasma con centration, indicating a primary role of drug absorption in the delivery of these systemically administered antibiotics to the site of action in perio dontal therapy The average GCF concentration in individuals varied widely ( between 0 and 8 mu g/ml) with approximately 50% of samples not achieving le vels of 1 mu g/ml. Conclusions: These observations suggest that poor absorption of orally-admi nistered tetracyclines in many individuals may account for much of the vari ability in clinical response to antibiotics observed in practice.