Niacin

Niacin
Kekulé, skeletal formula of niacin
Ball and stick model of niacin
Names
Pronunciation /ˈnəsɪn/
Preferred IUPAC name
Pyridine-3-carboxylic acid[1]
Other names
  • Nicotinic acid (INN)
  • Bionic
  • Vitamin B3
  • Vitamin PP
Identifiers
3D model (JSmol)
3DMet
109591
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.000.401
EC Number
  • 200-441-0
3340
KEGG
MeSH Niacin
RTECS number
  • QT0525000
UNII
  • InChI=1S/C6H5NO2/c8-6(9)5-2-1-3-7-4-5/h1-4H,(H,8,9) Y
    Key: PVNIIMVLHYAWGP-UHFFFAOYSA-N Y
  • InChI=1/C6H5NO2/c8-6(9)5-2-1-3-7-4-5/h1-4H,(H,8,9)
    Key: PVNIIMVLHYAWGP-UHFFFAOYAA
  • OC(=O)c1cccnc1
Properties
C6H5NO2
Molar mass 123.111 g·mol−1
Appearance White, translucent crystals
Density 1.473 g cm−3
Melting point 237 °C; 458 °F; 510 K
18 g L−1
log P 0.219
Acidity (pKa) 2.0, 4.85
Isoelectric point 4.75
1.4936
0.1271305813 D
Thermochemistry
−344.9 kJ mol−1
−2.73083 MJ mol−1
Pharmacology
C04AC01 (WHO) C10BA01 (WHO) C10AD02 (WHO) C10AD52 (WHO)
License data
Intramuscular, by mouth
Pharmacokinetics:
20–45 min
Hazards
GHS pictograms
GHS Signal word Warning
H319
P264, P280, P305+351+338, P337+313, P501
NFPA 704 (fire diamond)
1
1
0
Flash point 193 °C (379 °F; 466 K)
365 °C (689 °F; 638 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y verify (what is YN ?)
Infobox references
Niacin
INN: Nicotinic acid
Clinical data
Trade namesNiacor, Niaspan, others
AHFS/Drugs.comMonograph
MedlinePlusa682518
License data
Pregnancy
category
Legal status
Legal status
  • US: OTC / Rx-only
Identifiers
PDB ligand
CompTox Dashboard (EPA)
ECHA InfoCard100.000.401

Niacin, also known as nicotinic acid, is an organic compound and a form of vitamin B3, an essential human nutrient.[3] It can be manufactured by plants and animals from the amino acid tryptophan.[4] Niacin is obtained in the diet from a variety of whole and processed foods, with highest contents in fortified packaged foods, meat, poultry, red fish such as tuna and salmon, lesser amounts in nuts, legumes and seeds.[3][5] Niacin as a dietary supplement is used to treat pellagra, a disease caused by niacin deficiency. Signs and symptoms of pellagra include skin and mouth lesions, anemia, headaches, and tiredness.[6] Many countries mandate its addition to wheat flour or other food grains, thereby reducing the risk of pellagra.[3][7]

The amide derivative nicotinamide (niacinamide) is a component of the coenzymes nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP+). Although niacin and nicotinamide are identical in their vitamin activity, nicotinamide does not have the same pharmacological, lipid-modifying effects or side effects as niacin, i.e., when niacin takes on the -amide group, it does not reduce cholesterol nor cause flushing.[8][9] Nicotinamide is recommended as a treatment for niacin deficiency because it can be administered in remedial amounts without causing the flushing, considered an adverse effect.[10]

Niacin is also a prescription medication.[11] 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 niacin. 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.[11] Despite the proven lipid changes, niacin has not been found useful for decreasing the risk of cardiovascular disease in those already on a statin.[12] A 2010 review had concluded that niacin was effective as a mono-therapy,[13] but a 2017 review incorporating twice as many trials concluded that prescription niacin, while affecting lipid levels, did not reduce all-cause mortality, cardiovascular mortality, myocardial infarctions, nor fatal or non-fatal strokes.[14] Prescription niacin was shown to cause hepatotoxicity[15] and increase risk of type 2 diabetes.[16][17] Niacin prescriptions in the U.S. had peaked in 2009, at 9.4 million, declining to 1.3 million by 2017.[18]

Niacin has the formula C
6
H
5
NO
2
and belongs to the group of the pyridinecarboxylic acids.[3] As the precursor for nicotinamide adenine dinucleotide and nicotinamide adenine dinucleotide phosphate, niacin is involved in DNA repair.[19]