Response to nicotinic acid

The reason for the absence of an additive response to nicotinic acid plus nicotinamide, seen with whole blood and in recovery experiments, remains obscure. Nicotinic acid and nicotinamide seem to interfere with each other s utilization. There may exist a competition between nicotinic acid and nicotinamide for methylation growth therefore would not reach an algebraic sum when the two are combined because of the limited number of methyl groups available for these compounds. 

Nicotinic acid is used as a vasodilator. The flush reaction to nicotinic acid which occurs very rapidly is highly characteristic. The biochemical mechanism of the vascular response to nicotinic acid is not well understood. However, some reports suggest that nicotinic acid somehow enhances the biosynthesis or release of prostaglandin El, which stimulates adenylate cyclase and raises the level of cAMP (15). Wilson and Douglass (16) reported that the amount of nicotinic acid per injection should be <200 mg because the injection of 250 mg nicotinic acid to humans causes very severe flushing. 

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