Salicylate-induced occult gastrointestinal blood loss: comparison between different oral and parenteral forms of acetylsalicylates and salicylates.

Gastrointestinal fecal blood loss, determined by injecting 51Cr-labelled autologous red blood cells, was measured in 191 orthopaedic patients after oral or parenteral intake of different forms of acetylsalicylates or salicylates. Oral or parenteral administration of non-acetylated salicylates caused nearly no gastrointestinal bleeding, but the anti-inflammatory activity of these products can be questioned since they cannot inhibit prostaglandin synthetase. Buffered, soluble forms of acetylsalicylates caused gastrointestinal bleeding in more than 50% of the patients. However, enteric-coated and intravenous forms resulted in significantly less gastrointestinal bleeding. For both preparations a relationship between serum salicylate level and amount of fecal blood loss was found in the group of "bleeders" (an upper limit of physiological blood loss could definitely be determined by this method). The findings suggested a similar mode of action of enteric-coated and intravenous acetylsalicylates on gastric mucosa through a systemic action. It was concluded that in long-term anti-inflammatory salicylate treatment, enteric-coated forms are probably the galenic form of first choice.