Influence of Implants Composition on Melatonin Release from Ethylcellulose Matrix.

Background: Melatonin release from Ethylcellulose matrix has never been studied on the whole range of compositions. Objective: To perform a comprehensive study about the influence of the melatonin loading on its release from solid ethylcellulose implants, from both a kinetic and structural point of view. Method: Cylindrical implants differing in their Melatonin:Ethylcellulose ratio were fabricated to cover a large range of compositions. Drug release was assayed by in vitro dissolution tests in CTAB micellar solutions. The 2D imaging of implant chemical composition during Melatonin release was performed by confocal Raman spectroscopy. FT-IR spectroscopy and Karl-Fisher technique were employed to study implants hydration. Results: A drug radial leakage, whatever the implant composition, is imaged. The apparent diffusion coefficient, D of melatonin was evaluated considering Fickian radial diffusion: its value ranges from 2 to 6 10(-12) cm(2)/s depending on the EC content. The variation of the characteristic drug delivery time with composition was non-monotonous and two different regimes were identified. Conclusion: A micellar transport of Melatonin was found. The two regimes in drug release were interpreted considering the polymer barrier effect, the initial porosity and M domains connectivity.