Endoscopic assessment of the effects of dipyrone (metamizol) in comparison to paracetamol and placebo on the gastric and duodenal mucosa of healthy adult volunteers.

The potentially damaging gastric and duodenal effects of dipyrone, a nonnarcotic analgesic agent, were evaluated in three phases in comparison to placebo and paracetamol. Three groups of 12 healthy adult volunteers were treated in a double-blind study, according to a cross-over, randomization sequence, using the double-dummy technique, for two 15-day periods, with dipyrone 3 g/day and placebo (group I), dipyrone 1.5 g/day and placebo (group II), and dipyrone 1.5 g/day and paracetamol 1.5 g/day (group III). An esophagogastroduodenoscopy was performed at the beginning and end of each treatment period. In the first treatment group, grade-3 and 4 mucosal lesions were found after dipyrone administration (3 g/day) in 3 of 12 (25%) subjects (multiple antral erosions, gastric ulcer and duodenal ulcer, 1 case each), whereas grade-2 mucosal lesions (antral erosions) were detected in 1 of 12 cases (8%) after the corresponding placebo treatment. The difference between the two treatments, however, was not statistically significant (p > 0.05). Only in the gastric ulcer case were subjective symptoms reported (feeling of hunger). At the 1.5-g/day dose (groups II and III), dipyrone produced no gastroduodenal lesions, the endoscopic results showing no appreciable difference between dipyrone and either placebo (p = 0.54) or paracetamol (p = 0.99). No subjective symptoms were reported in any of these subjects. Dipyrone, administered for 2 weeks, has effects on the gastric and duodenal mucosa comparable to those of paracetamol and placebo, though noticeable damage is detectable at a dosage of 3 g/day.