Chronobiotic Hormone Melatonin: Comparative in vitro Release Studies from Matrix Tablets and Liposomal Formulations

Background: Melatonin, a hormone synthesised by the pineal gland, has a significant role in the regulation of the circadian biological clock. Objective: The present study aims at investigating how matrix tablets comprised of common hydrogels influence the release profile of melatonin at both physiological pH's. Moreover, we designed and developed liposomes incorporating this hormone in order to compare its release profile. Methods: Preparation of matrix tablets and liposomal formulations. Drug release studies. Results: Hydrogel based matrix tablets of the chronobiotic hormone melatonin were developed aiming at effecting its sustained release at pH 1.2 and 7.4. The matrix tablets used were comprised of hydroxypropyl methylcellulose (HPMC) and dextran. Moreover, melatonin was encapsulated into conventional liposomes composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and dipalmitoyl-phosphatidyl glycerol (DPPG), in an attempt to compare the hormone's release profile from liposomal formulations with its respective release from matrix tablets. Conclusion: Both liposomal and solid pharmaceutical formulations, albeit their different mechanistic drug-leaching mode of action, are suitable for treating sleep onset problems and/or sleep maintenance discomforts.