vitamin b3 vitamin b3 vitamin b3, colloquially referred to as niacin, is a vitamin family that includes three forms or vitamers: niacin (nicotinic acid), nicotinamide (niacinamide), and nicotinamide riboside. all three forms of vitamin b3 are converted within the body to nicotinamide adenine dinucleotide (nad). nad is required for human life and people are unable to make it within their bodies without either vitamin b3 or tryptophan. nicotinamide riboside was identified as a form of vitamin b3 in 2004. vitamin b3drug classstructure of nicotinamide, one of the vitamers of vitamin b3class identifiersusevitamin b3 deficiencyatc codea11hbiological targetenzyme cofactorclinical datadrugs.comniacin