Thermosetting microemulsions and mixed micellar solutions as drug deliverysystems for periodontal anesthesia

In the present study, thermosetting microemulsions and mixed micellar solut ions were investigated as drug delivery systems for anesthetizing the perio dontal pocket. The structure of the systems, consisting of the active ingre dients lidocaine and prilocaine. as well as two block copolymers (Lutrol(R) F127 and Lutrol(R) F68), was investigated by NMR spectroscopy and photon c orrelation spectroscopy (PCS). The results obtained for dilute (1-3% w/w) s olutions show discrete micelles with a diameter of 20-30 nm and a critical micellization temperature of 25-35 degrees C. Gel permeation chromatography (GPC) was used to study the distribution of the active ingredients, and in dicates a preferential solubilization of the active components in micelles over unimers. Analogous to the Lutrol(R) F127 single component system these formulations display an abrupt gelation on increasing temperature. The gel ation temperature was found to depend on both the drug ionization and conce ntration. These systems have several advantages over emulsion-based formula tions including good stability, ease of preparation. increased drug release rate, and improved handling due to the transparency of the formulations. ( C) 2000 Elsevier Science B.V, All rights reserved.