Niacin is a water-soluble vitamin, which is also known as nicotinic acid or vitamin B3. Niacin is a dietary precursor of nicotinamide adenine dinucleotide (NAD), which is essential for oxidation-reduction reactions, DNA repair, lipid metabolism, and ATP synthesis. Niacin SR 500mg delivers a slow release of niacin over several hours that help avoid the uncomfortable flushing action normally experienced with regular niacin dosing.