Comparative effects of nicotinic acid and nicotinamide on cholera toxin-induced secretion in rabbit ileum

Nicotinic acid reduces the cholera-toxin induced fluid secretion in experimental animals but its toxicity at high doses prevent its therapeutic use in patients suffering from cholera. This study aimed to determine whether nicotinamide, the non toxic amide derivative of nicotinic acid, is as effective as nicotinic acid in inhibiting cholera toxin induced intestinal secretion in vivo. Four intestinal loops, with their blood supply intact, were isolated in 30 rabbits and injected with either (i) 30 mM mannitol, (ii) 30 mM mannitol + 10 micrograms cholera toxin, (iii) 30 mM glucose, or (iv) 30 mM glucose + 10 micrograms cholera toxin. These rabbits were then randomly assigned to three groups receiving intraluminally either 100 mg/kg of nicotinic acid, 100 mg/kg of nicotinamide, or 10 ml/kg of Ringer solution. Measurement of intestinal fluid accumulation showed that nicotinic acid, but not nicotinamide, significantly reduced cholera toxin induced intestinal secretion.