In vitro oxidation of uric acid in serum by methylene blue.

Methylene blue oxidizes uric acid to allantoin in vitro, analogous to the reaction between uric acid and phosphotungstate, although the rate is considerably slower. The reaction requires oxygen and produces hydrogen peroxide. As little as 10 micromol of methylene blue per liter in a serum sample will produce a measurable difference in the apparent uric acid concentration within 4 h at room temperature. Methylene blue may be administered for various medical reasons. If uric acid is to be measured in such sera, the procedure should be performed within 30 min, whatever method of analysis is used.