Fecal blood loss and plasma salicylate study of salicylsalicylic acid and aspirin.

Using a placebo-controlled methodology, 20 healthy volunteers housed in a clinical research facility for 23 days were studied for fecal blood loss and plasma salicylate levels after taking salsalate (salicylsalicylic acid) or aspirin. Daily dosages were 3000 mg salsalate or 3900 mg aspirin. Aspirin produced statistically significant gastrointestinal blood loss over control levels and over that produced by salsalate (P less than 0.01). Blood loss with salsalate was not different than that with placebo. Despite the intentional disparity of dosages between the two drugs, plasma salicylate levels were not statistically different. Side effects occurred at about equal frequency with either drug. Most prominent were headache and nausea. However, concomitant upper respiratory infection in 12 subjects rendered interpretation difficult.