The Collaborative International Dictionary of English v.0.48:

nicotinic acid \nic`o*tin"ic ac"id\, n. (Chem.)
   An organic acid (C6H5NO2), a carboxylated derivative of
   pyridine, obtained by the oxidation of nicotine; called also
   niacin and antipellagra vitamin, and vitamin B5.
   Chemically it is 3-pyridinecarboxylic acid.

   Note: It is a cofactor in several enzymatic reactions, and is
         used to prevent a pellagra-like disease in dogs.
         --[MI11]

   Syn: 3-pyridinecarboxylic acid, niacin, antipellagra vitamin.
        [1913 Webster +PJC]

The Collaborative International Dictionary of English v.0.48:

vitamin B5 \vitamin B5\ n.
   See nicotinic acid.

   Syn: nicotinic acid.
        [PJC]