NSAID-associated gastrointestinal damage: methodological considerations and a review of the experience with enteric coated naproxen.

Various methods are available for investigating gastrointestinal adverse effects of NSAIDs. Upper endoscopy is regarded a gold standard for controlled studies, but the grading and categorization of the visual impression of mucosal changes is complicated. Faecal blood loss represents another aspect of the toxicity, but quantitative measurements require the cumbersome procedure of 51Cr-labelling of red blood cells. For monitoring distal gut effects, permeability tests can be applied, and combination of tracer substances may further enhance the method. Measurements of electrical potential differences over the gastric mucosa are also available to monitor functional aspects of the gastric mucosal integrity. Controlled endoscopic trials have indicated an advantage of enteric coated naproxen tablets over plain tablets. Distal transfer of the toxicity by small bowel release of the active substance, has not been confirmed by permeability tests.