Controlled release of bilayer tablet comprising vitamin B6 rapid-release layer and melatonin sustained-release layer

Here, the formulation of a novel bilayer tablet comprising a vitamin B6 rapid-release layer and a melatonin sustained-release layer is described. The effects of viscosity and concentration of the sustained-release matrix material, amount of diluent, and melatonin particle size on the release characteristics of melatonin were examined. In addition, the drug-release behavior of the prepared bilayer tablets was examined in different dissolution media. Further, drug-release kinetics and melatonin behavior in the sustained-release layer were evaluated based on dissolution profiles and changes in tablet weight during dissolution. Furthermore, the stability of the bilayer tablet was established. The in vitro release test revealed that vitamin B6 was completely released within 10–15 ​min, with melatonin demonstrating ∼90% cumulative release within 8 ​h. Based on kinetic model fitting results, melatonin release was well fitted to the Ritger-Peppas model; the release mechanism was non-Fick diffusion with both diffusion and erosion. The drug-release study confirmed that the melatonin sustained-release layer predominantly underwent polymer swelling rather than polymer erosion. The stability test results showed that the bilayer tablets had good stability under high temperature, high humidity, and light conditions. The bilayer tablets offer an alternative for the controlled-release oral administration of melatonin, although their in vivo effects need to be investigated in human studies.