NICOTINIC ACID (NIACIN) 



pressure equivalent to 49,275 feet. The increase in respiratory rate 

 at low pressures was much less in treated than in untreated rats. 



Nicotinic acid, but not the amide, has a pronounced, though 

 transient, vasodilator action. This is the reason for the flushing and 

 tingling of the skin and rise in the cutaneous temperature when nico- 

 tinic acid is taken orally. The effect may be somewhat alarming for 

 patients who have not been warned to expect it, but it soon passes 

 off. Nicotinamide does not have this effect.'^ The vasodilator action 

 of nicotinic acid is of value in conditions where it is desirable to 

 increase the peripheral blood flow, such as gangrene of the mouth and 

 indolent ulcers. It also accounts for the ability of nicotinic acid to 

 relieve severe idiopathic headache and migraine.^ Nicotinic acid, 

 but not nicotinamide, increased the intracranial blood flow in human 

 subjects, the effect running parallel with the flushing of the skin.^ 



Nicotinamide was without effect on the blood sugar levels in normal 

 subjects and in diabetic patients. ^^ Nicotinic acid and nicotinamide 

 stimulated bile secretion, and the former also increased the serum 

 bilirubin and the excretion of urobilin.^^ 



References to Section 13 



1. K. K. Chen, C. L. Rose and E. B. Robbins, Proc. Soc. Exp. Biol. 



Med., 1938, 38, 241. 



2. K. Unna, /. Pharmacol., 1939, 65, 95- 



3. F. G. Brazda and R. A. Coulson, Proc. Soc. Exp. Biol. Med., 1946, 



62, 19. 



4. P. Ellinger, G. Fraenkel and M. M. Abdel Kader, Biochem. J., 



1947. 41, 559. 



5. N. W. Shock and W. H. Sebrell, Amer. J. Physiol., 1946, 146, 52. 



6. R. M. Calder, Proc. Soc. Exp. Biol. Med., 1947, 65, 76 ; 1948, 



68, 642. 



7. H. Field and W. D. Robinson, Amer. J. Med. Sci., 1940, 199, 275. 



8. J. W. Goldzierer and G. L. Popkin, /. Amer. Med. Assoc, 1946, 



131, 103- 



9. C. D. Aring, H. W. Ryder, E. Roseman, M. Rosenbaum and E. B. 



Ferris, Arch. Neurol., Psychiat., 1941, 46, 649. 



10. J. N. Cumings, Brit. Med. J., 1947, 2, 613. 



11. M. Stefanini, /. Lah. Clin. Med., 1949, 34, 1039. 



14. FUNCTION OF NICOTINIC ACID 



Coenzymes I and n 



By an unusual inversion of the customary course of events, the 

 biological significance of nicotinic acid was understood before its im- 

 portance in hiunan nutrition was appreciated, for in 1935 O. Warburg 



274 



