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 United States had peaked in 2009 at 9.4 million, declining to 800 thousand by 2020. In 2023, it was the 288th most commonly prescribed medication in the US, with more than 500,000 prescriptions.

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.