Measurement of N tau-methylhistamine concentrations in urine as a parameter for histamine release by radiographic contrast media.

In a group of 750 patients who were admitted for excretory urography using iodamide, 14 distinct adverse reactions were observed. 2 of these patients exhibited a severe reaction, 4 a moderate reaction and 8 a mild reaction. In the urine portions collected 1 h after the administration of the contrast medium N tau-methylhistamine (an important histamine metabolite) was elevated both in patients showing severe adverse reactions and in those with moderate reactions. There was a rather good correlation between the increase of urinary N tau-methylhistamine concentrations and the severity of the reaction to iodamide.