Gastrointestinal blood loss of oxaprozin and aspirin with placebo control.

The objective of this study was to compare the effects of oxaprozin (4,5-diphenyl-2-oxazolepropionic acid), a nonsteroidal, antiinflammatory compound, and aspirin in a double-blind, placebo-controlled study to estimate gastrointestinal bleeding. The determination of fecal blood loss was made quantitatively by the use of the radioactive (51Cr) technique. During the first week, subjects were controlled with and without placebo. At the end of the second week, the subjects were divided and randomly assigned to one of three groups; 10 received 1200 mg oxaprozin (600 mg twice daily), 11 received 3900 mg aspirin (975 mg four times a day), and the remaining 8 subjects received placebo for two weeks. During the last two weeks, all received placebo again. A statistical analysis of variance showed that there were no statistical differences between the groups during the first and last two weeks of placebo therapy. During the active treatment period, weeks 3 and 4, there were statistically significant differences among the three groups. The mean blood loss during week 3 was significantly greater for the aspirin group, 8.8 ml/day, than the oxaprozin group, 3.3 ml/day (P less than 0.05), and the placebo group, 1.4 ml/day (P less than 0.001). The smaller difference between oxaprozin and placebo was also significant (P less than 0.05). During the fourth week, the mean daily blood loss among oxaprozin patients had decreased to 2.3 ml/day, and no statistically significant difference from placebo (1.1 ml/day) was found.