Melatonin Bioavailability After Oral Administration of a New Delayed-Release Form in Healthy Male Volunteers.

Background: Two main types of galenic formulation, immediate release and prolonged release, have been developed to optimize melatonin bioavailability. We recently described the kinetic profile of a prolonged-release form generating a peak of plasma melatonin 1 h (T_max) after intake, followed by a prolonged decay over time. We have developed a new oral form of melatonin with the aim of producing a melatonin peak several hours after intake.

Objective: The objective is to investigate melatonin bioavailability after administration of this new delayed-release form (DR form).

Methods: In this single-centre open-label study, 12 healthy male volunteers received one tablet of the DR form containing 1.9 mg melatonin, 10 mg zinc and 200 mg lemon balm extract (Melissa officinalis L aerial parts). Blood samples were collected for 12 h, beginning at 8:00 am. Plasma concentrations of melatonin and 6-sulfatoxymelatonin (6-SMT), the main hepatic melatonin metabolite, were determined by radioimmunoassay.

Results: A progressive increase in plasma melatonin concentrations was observed from 20 min and a peak about 3 h after intake (C_max 740 ± 824 pg/mL; T_max 179 ± 60 min). Concentrations remained high between 140 and 220 min, the concentration remaining physiologically significant (over 100 pg/mL) up to 7 h after intake. The DR form was well tolerated.

Conclusions: The melatonin release profile was consistent with what was anticipated for the DR form. The DR form generated a 2 h delayed T_max compared with a prolonged-release form previously evaluated. This suggests that the DR form is suitable for the treatment of certain sleep disorders such as short sleep duration or early awakening.

Trial registry: Registration number: NCT05419466.