Reduction of Surgery-induced Peritoneal Adhesions by Methylene Blue

Background: The possible involvement of inflammatory mediators such as nitric oxide (NO), and reports of protective effects of antioxidants, led us to test the effectiveness of methylene blue and NO synthesis inhibitor in reducing adhesion formation. Methods: Generation of adhesions in rats, by scraping the anterior uterine horn wall, was followed by intraperitoneal administration of saline, methylene blue, or Nα-t-BOC-ω-nitro-L-arginine. Additional rats received identical treatments, but without the serosal damage. Two weeks later, formation of adhesions was quantitatively graded. Results: Adhesions were found in <5% of the rats with the sham surgery, regardless of treatment. In the experimental group, >95% of the rats treated with saline or NO synthetase inhibitor had severe adhesions, in contrast to 5% of the methylene blue treated rats. Severity of adhesion was lower in the methylene blue group (P<0.001). Conclusions: Methylene blue was very effective in preventing formation of peritoneal adhesions. Its activity is probably through inhibition of free-radical generation and not of nitric oxide action.