Phase 1 evaluation of a local delivery device releasing silver ions in periodontal pockets: safety, pharmacokinetics and bioavailability.

A new local delivery device (LDD) capable of releasing silver in periodontal pockets has been developed and tested pre-clinically. Silver has potent antimicrobial effects on Gram-negative periodontal pathogens with a mean in vitro minimum bactericidal concentration (MBC) < or =0.5 microg/ml. This phase 1 study assessed the safety, pharmacokinetics and bioavailability of silver ions delivered intracrevicularly with a resorbable LDD (PocketGuard) in a group of 9 volunteers affected with periodontitis. In each subject, a PLGA/PEG LDD loaded with 12% silver nitrate (w/w) was inserted in each of 4 selected pockets > or =5 mm. Serum, gingival fluid and subgingival plaque samples were evaluated before and at various time points after LDD placement for 21 days. At each time point, the concentration of silver in gingival crevicular fluid (GCF) was quantified with an Inductively Coupled Plasma-Mass Spectrometer. Subgingival plaque samples were processed for evaluation of total anaerobic and aerobic counts (CFU/ml). The maximum mean silver concentration in GCF was 1,493 +/- 709 microg/ml (range 589-2,245). It decayed exponentially with a half-life of 7.1 +/- 6.1 days (2.7-20.4). Average silver concentrations in excess of 10 microg/ml were detected in each patient for 14 days after LDD placement with the average concentration for all patients in excess of 25 microg/mL at day 21. Total anaerobic counts decreased an average of 1.7 +/- 1.9 x 10(6) CFU/ml (p= 0.0078) from baseline to day 7, indicating that the silver was biologically active. A mild increase in cervical root discoloration was observed at day 21:0.25 +/- 0.31 stain index units. Discoloration that did not resolve spontaneously could be removed at the end of the study with polishing. No systemic effects were observed. It is concluded that local silver concentrations above the MBC in serum were maintained for at least 21 days. A specific microbiologic effect was also observed.