Antinociceptive effects, metabolism and disposition of ketamine in ponies under target-controlled drug infusion

Ketamine is widely used as an anesthetic in a variety of drug combinations in human and veterinary medicine. Recently, it gained new interest for use in long-term pain therapy administered in sub-anesthetic doses in humans and animals. The purpose of this study was to develop a physiologically based pharmacokinetic (PBPk) model for ketamine in ponies and to investigate the effect of low-dose ketamine infusion on the amplitude and the duration of the nociceptive withdrawal reflex (NWR). A target-controlled infusion (TCI) of ketamine with a target plasma level of 1 microg/ml S-ketamine over 120 min under isoflurane anesthesia was performed in Shetland ponies. A quantitative electromyographic assessment of the NWR was done before, during and after the TCI. Plasma levels of R-/S-ketamine and R-/S-norketamine were determined by enantioselective capillary electrophoresis. These data and two additional data sets from bolus studies were used to build a PBPk model for ketamine in ponies. The peak-to-peak amplitude and the duration of the NWR decreased significantly during TCI and returned slowly toward baseline values after the end of TCI. The PBPk model provides reliable prediction of plasma and tissue levels of R- and S-ketamine and R- and S-norketamine. Furthermore, biotransformation of ketamine takes place in the liver and in the lung via first-pass metabolism. Plasma concentrations of S-norketamine were higher compared to R-norketamine during TCI at all time points. Analysis of the data suggested identical biotransformation rates from the parent compounds to the principle metabolites (R- and S-norketamine) but different downstream metabolism to further metabolites. The PBPk model can provide predictions of R- and S-ketamine and norketamine concentrations in other clinical settings (e.g. horses).

Anti-infective therapy of peri-implantitis with adjunctive local drug delivery or photodynamic therapy: 12-month outcomes of a randomized controlled clinical trial

OBJECTIVE: The objective of the study is to compare the clinical, microbiological and host-derived effects in the non-surgical treatment of initial peri-implantitis with either adjunctive local drug delivery (LDD) or adjunctive photodynamic therapy (PDT) after 12 months. MATERIALS AND METHODS: Forty subjects with initial peri-implantitis, that is, pocket probing depths (PPD) 4-6 mm with bleeding on probing (BoP) and radiographic bone loss ≤2 mm, were randomly assigned to two treatment groups. All implants were mechanically debrided with titanium curettes and with a glycine-based powder airpolishing system. Implants in the test group (N = 20) received adjunctive PDT, whereas minocycline microspheres were locally delivered into the peri-implant pockets of control implants (N = 20). At sites with residual BoP, treatment was repeated after 3, 6, 9 and 12 months. The primary outcome variable was the change in the number of peri-implant sites with BoP. Secondary outcome variables included changes in PPD, clinical attachment level (CAL), mucosal recession (REC) and in bacterial counts and crevicular fluid (CF) levels of host-derived biomarkers. RESULTS: After 12 months, the number of BoP-positive sites decreased statistically significantly (P < 0.05) from baseline in both groups (PDT: 4.03 ± 1.66-1.74 ± 1.37, LDD: 4.41 ± 1.47-1.55 ± 1.26). A statistically significant (P < 0.05) decrease in PPD from baseline was observed at PDT-treated sites up to 9 months (4.19 ± 0.55 mm to 3.89 ± 0.68 mm) and up to 12 months at LDD-treated sites (4.39 ± 0.77 mm to 3.83 ± 0.85 mm). Counts of Porphyromonas gingivalis and Tannerella forsythia decreased statistically significantly (P < 0.05) from baseline to 6 months in the PDT and to 12 months in the LDD group, respectively. CF levels of IL-1β decreased statistically significantly (P < 0.05) from baseline to 12 months in both groups. No statistically significant differences (P > 0.05) were observed between groups after 12 months with respect to clinical, microbiological and host-derived parameters. CONCLUSIONS: Non-surgical mechanical debridement with adjunctive PDT was equally effective in the reduction of mucosal inflammation as with adjunctive delivery of minocycline microspheres up to 12 months. Adjunctive PDT may represent an alternative approach to LDD in the non-surgical treatment of initial peri-implantitis.

Development of light-responsive porous polycarbonate membranes for controlled caffeine delivery

For controlled caffeine release, light-responsive membranes were developed. It was possible to produce membranes that reduced their caffeine permeability resistance by about 97% when irradiated with UV-light compared to measurements at daylight. This was achieved by grafting polymers possessing photochromic units onto track-edged polycarbonate membranes. Covalently linked coatings on porous polycarbonate membranes were obtained by plasma activation of the membrane surface followed by plasma-induced graft polymerization. Copolymerization of spiro-compounds during the coating process as well as postmodification of preformed coatings with spiropyran resulted in photochromic membranes. For the copolymerization process, the synthesis of five photochromic methacrylic and acrylic spiropyrans and spirooxazines was successfully performed. Additionally, a spiropyran with carboxylic acid functionality was synthesized for the postmodification process. This enabled us to postmodify polymeric materials containing alcohol or amine groups to obtain photochromic materials. UV-irradiation of these light-responsive membranes resulted in a strong colouration of the membrane, in a reduction of surface tension, which resulted in a decreased caffeine permeability resistance. The membranes were characterized using XPS for the elemental composition of the coating, contact angle measurements for the surface tension, solid-state UV/VIS measurements for the determination of the kinetic and stability properties, and two-photon microscopy for the localisation of the photochromic substance in the porous membrane.