Comparative evaluation of gastrointestinal blood loss in the feces of rats following pepto-bismol liquid and aspirin administration

Acetylsalicylic acid (aspirin) can irritate the gastrointestinal tract of man and of animals ultimately resulting in hemorrhagic erosions and ulcers. Since Pepto-Bismol liquid also contains salicylates (primarily bismuth subsalicylate), the relative sensitivity of the GI tract of the rat to hemorrhage and subsequent blood loss in response to Pepto-Bismol and to aspirin was determined. The appearance of blood in the feces of male Sprague-Dawley rats 22 hr after the peroral administration of aspirin or Pepto-Bismol at equivalent salicylate doses was measured spectrophotometrically using the modified benzidine assay. Aspirin, administered in total salicylate doses of 38.4, 57.5, 76.7 or 153 mg/kg caused a dose-dependent increase in blood loss ranging from 53 to 276 μl/kg body weight, the latter 2 values being significantly different from control. Pepto-Bismol at total salicylate doses of 38.4, 57.5 or 76.7 mg/kg failed to cause blood loss. Neither Pepto-Bismol nor aspirin obscured recovery of orally-dosed blood in rat feces. The sensitivity of the benzidine assay allowed for the quantitative assessment of 5 μl or less blood per gram of feces. It was concluded that at equivalent salicylate dose levels, Pepto-Bismol, unlike aspirin, did not cause a dose-dependent increase in blood in the feces of rats, suggesting that salicylates should not be collectively categorized as inducing gastric mucosal damage.