Microdialysis as a tool to determine the skin concentration of mometason furoate in rats.

The objective of this study was to investigate the feasibility of microdialysis as a tool to determine the skin concentration of mometason furoate (MF), a lipophilic and highly protein-bound compound. The relative recovery (RR) of mometasone furoate was determined by an in vitro no-net-flux method using three different perfusates (40% PEG400, 5% fat emulsion, and 20% fat emulsion) and four flow rates (0.5, 1, 2, and 4 µL x min(-1)). With the increasing of flow rate, the relative recovery was decreased from 48.8% to 3.1%. The in vitro recovery was increased to 23.71%, 42.76% and 56.21% when 40% PEG400, 5% fat emulsion or 20% fat emulsion was used as microdialysis perfusates, respectively. Fat emulsion (5%) was chosen as the perfusate to evaluate the in vivo recovery by a retrodialysis method, in which mometasone furoate concentration in different tissues was determined. The result showed that concentrations of mometasone furoate in the dermis was greater than that in the subcutaneous or muscle tissue. It was concluded that a recovery enhancer could be used in microdialysis technique, especially for determining skin concentrations of lipophilic and high protein-bounds.

Controlled release of huperzine A from biodegradable microspheres: In vitro and in vivo studies.

The objective of the present work was to further study the in vitro characteristics, in vivo pharmacokinetics and pharmacodynamics of huperzine A (HupA) loaded biodegradable microspheres designed for sustained release of HupA over several weeks. A conventional o/w emulsion-solvent evaporation method was used to incorporate HupA, which is of interest in the palliative treatment of Alzheimer's disease (AD), into end-group uncapped poly(D,L-lactide-co-glycolide) (PLG-H). A prolonged in vitro drug release profile was observed, with a complete release of the incorporated drug within 5-6 weeks. The in vivo pharmacokinetics study of HupA loaded microspheres showed sustained plasma HupA concentration-time profile after subcutaneous injection into rats. The pharmacodynamics evaluated by determination of the activity of acetylcholinesterase in the rat cortex also showed a prolonged pharmacological response. Both the in vitro release and in vivo pharmacological responses correlated well with the in vivo pharmacokinetics profile. The results suggest the potential use of HupA-loaded biodegradable microspheres for treatment of AD over long periods.

[Percutaneous absorption of meloxicam patches in hairless mouse].

Meloxicam concentration in skin was determined following topical administration of meloxicam patches in hairless mouse. Samples were analysized by HPLC coupled with microdialysis sampling technique, in which in vivo recovery of probe was characterized by the retrodialysis method. It was indicated that the in vivo recovery of the probe was 14.0%. The range of steady state concentration of meloxicam in dialysate was 24-50 ng x mL(-1), and that was 170-360 ng x mL(-1) in the hairless mouse skin. Steady state concentration of meloxicam was reached shortly after the application of meloxicam patches, which was maintained during the period of experiment.