TOXICITY STUDIES ON TANNIC ACID ADMINISTERED BY ENEMA

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Abstract
1. After intraperitoneal administration of tannic acid to rats, the dose sufficient to cause hepatotoxicity in 50 per cent of the animals (HD50) is in the region of 50 mg./kg.; the HD0 is 40 mg./kg. 2. After intraperitoneal injection, gallic acid produces no hepatotoxic response, even at lethal levels. The cause of death in these cases is due to renal damage. 3. Tannic acid could not be detected in the portal vein blood samples after instillation of 1 per cent tannic acid enemas even though retained for 1 hour. Minute amounts of tannic acid were detected in the portal vein blood samples after instillation of 2 per cent tannic acid enemas forcibly retained for 1 minute. 4. Increased concentration of tannic acid in the enema and a longer period of colonic exposure result in increased amounts of intact tannic acid being detected in the portal venous blood. 5. Although intact tannic acid could be detected in blood samples from the thoracic inferior vena cava following a 16 per cent tannic acid enema maintained in the colon for 15 minutes, it could not be detected when the enema was maintained for 1 minute. In contrast, gallic acid could be detected at both time periods. This suggests that the nonspecific methods utilized to detect tannic acid in the blood, as reported previously, resulted in the detection of gallic acid rather than of tannic acid.