Determination of urinary formaldehyde following administration of methenamine salts.

C TJRRENT COLORIMETRIC METHODS for the measurement of formaldehyde in the presence of methenamine salts appear misleading. The principal problems with these technics include the release of formaldehyde (1, 2) from intact methenamine and the nonspecificity of the reaction producing color with other compounds present in urine. However, a modification of the method of Tannenbaum and Bricker (3) appeared suitable for assaying urinary formaldehyde in the presence of methenamine or its salts. Pretreatment with ammonia permits assaying formaldehyde in the presence of methenamine according to data presented below. In view of the analytical shortcomings in data presented in the past on formaldehyde production from methenamine and its salts, a study was undertaken to evaluate the actual formaldehyde release pattern in vivo of 4 methenamine preparations. Three methenamine salts, available commercially, were studied as well as methenamine itself. One of the methenamine preparations, methenamine mandelate was enteric coated while methenamine sulfosalicylate, methenamine hippurate, and methenamine itself were not. The study was further intended to ascertain the effect of this coating on the absorption characteristics of the drug.