Preparation and evaluation in vivo and in vitro of melatonin controlled-release bilayer tablets

Aim:To prepare melatonin controlled-release bilayer tablets and study its pharmaceutical characteristics.Methods:HPMC and stearic acid were used to prepare melatonin controlled-release bilayer tablets by application of solid dispersion method and double compression technology.In a randomized,crossover design,a single oral dose of melatonin tablets(3 mg) or melatonin controlled-release bilayer tablets(6 mg) was given to 6 Beagle dogs,plasma concentration of melatonin was detected by HPLC.Pharmacokinetic parameters were estimated by 3P97 pharmacokinetic program.Results:The peak levels(c_(max)) after administration of melatonin controlled-release bilayed tablets(6 mg) and melatonin tablets(3 mg) averaged(8.31±5.11) and(11.27±3.77)ng/mL at(1.00±0.37) and(0.50±0.18)h respectively.The mean elimination half lives(t_(1/2Ke)) were found to be(3.27±0.89) and(1.21±0.52) h respectively.AUC_(0～t) were calculated to be(38.03±16.45) and(25.23±7.71) ng/mL·h respectively.Conclusion:The formulated melatonin controlled-release bilayer tablets exhibited both controlled-and rapid-release characteristics in vitro.The bioavailability of melatonin controlled-release bilayer tablets was lower than that of conventional release tablets.There existed no significant difference in t_(max),but calculated MRT of controlled-release bilayer tablets was significantly greater than that of conventional release tablets.The in vitro release and in vivo absorption profiles were consistent with circadian rhythms in humans.There existed correlation between the in vitro release and in vivo absorption.