interviews David C. Brodner, MD,  about a study on REMfresh CRA-melatonin.

Other available products, such as immediate-release melatonin, help initiate the onset of sleep but are usually unable to sustain prolonged sleep maintenance due to an immediate burst of melatonin, which is quickly degraded due to its relatively short half-life (60 minutes). Absorption in the lower digestive tract is limited by melatonin’s limited ability to be absorbed in a low acidity or neutral pH environment.