Nicotinic acid (syn. niacine) is provitamine of nikotinamide, which is a part of coenzymes NAD+ (nicotinamide adenine dinucleotide) and NADP+ (nicotinamide adenine dinucleotide phosphate). Nicotinic acid was originally indicated for its vasodilating action.
Laropiprant as selective antagonist of prostaglandine receptors D2 (PGD2) can moderate vazodilatation causing by nicotinic acid.