Nicotinic acid

Nicotinic acid, or niacin, is an organic compound and a vitamer of vitamin B₃, an essential human nutrient. It is produced by plants and animals from the amino acid tryptophan.

Nicotinic acid is also a prescription medication. Amounts far in excess of the recommended dietary intake for vitamin functions will lower blood triglycerides and low density lipoprotein cholesterol (LDL-C), and raise blood high density lipoprotein cholesterol (HDL-C, often referred to as "good" cholesterol). There are two forms: immediate-release and sustained-release nicotinic acid. Initial prescription amounts are 500 mg/day, increased over time until a therapeutic effect is achieved. Immediate-release doses can be as high as 3,000 mg/day; sustained-release as high as 2,000 mg/day. Despite the proven lipid changes, nicotinic acid has not been found useful for decreasing the risk of cardiovascular disease in those already prescribed a statin drug. A 2010 review had concluded that nicotinic acid was effective as a mono-therapy, but a 2017 review incorporating twice as many trials concluded that prescription nicotinic acid, while affecting lipid levels, did not reduce all-cause mortality, cardiovascular mortality, myocardial infarctions, nor fatal or non-fatal strokes. Prescription nicotinic acid was shown to cause hepatotoxicity and increase risk of type 2 diabetes. Nicotinic acid prescriptions in the U.S. had peaked in 2009 at 9.4 million, declining to 800 thousand by 2020.

Nicotinic acid has the formula C
₆H
₅NO
₂ and belongs to the group of the pyridinecarboxylic acids. As the precursor for nicotinamide adenine dinucleotide and nicotinamide adenine dinucleotide phosphate, it is involved in DNA repair.

Extra-terrestrial nicotinic acid has been found in carbonaceous chondrite meteorites and in sample-returns from the asteroids 162173 Ryugu and 101955 Bennu.