In vitro release studies on lidocaine aqueous solutions, micellar solutions, and o/w emulsions
Brodin, A.; Nyqvist-Mayer, A.
Acta Pharmaceutica Suecica 19(4): 267-284
1982
ISSN/ISBN: 0001-6675 PMID: 7136735 Document Number: 185266
The initial and steady state of release, through a silicone membrane, of lidocaine from aqueous solutions, micellar solutions and emulsions with and without the presence of glass wool, were studied. Comparisons to the corresponding creams were made. The equilibrium conditions in the systems were characterized by filtration and gel chromatography to determine the partition coefficients to the oil and micellar phases. By using free unsolubilized lidocaine as the saturation concentration in an equation for suspensions, diffusion coefficients independent of the total concentration can be obtained when the oil drops are entrapped in a network formed by glass wool or by a gelling agent. This is not the case for micelles. Comparing the observed diffusion coefficients of different systems, the effect of the volume fraction of the dispersed phase both in emulsions and micellar solutions can be estimated qualitatively. The release process suggests that emulsion drops may interact with the membrane.