Development and characterization of an oral controlled-release delivery system for melatonin

Sugar spheres loaded with melatonin (MT) were coated with Aquacoat® to control the release rate of MT. Dissolution of MT was evaluated using the USP basket method. With 18-20 mesh beads, T(50%) (time to release 50% of drug) for 5%, 10%, and 20% coatings was 10 min, 35 min, and 60 min, respectively. A desired release pattern over 8 hours was obtained with 20% coating on 8-10 mesh beads. T(50%) for 5%, 10%, and 20% coatings was about 1, 2, and 4 hours, respectively. MT in 20% coated beads was quite stable during storage at room temperature with less than 5% MT degraded during 6 months of storage. Dissolution profiles from 8-10 mesh beads with a 20% coating were unchanged after 6 months of storage at room temperature. Administration of the dosage form to human subjects maintained MT plasma concentrations over 100 pg/ml for approximately 8 hours.