The Determination of Methenamine and its Salts in Tablet Dosage Forms Using Ion-Pair Extraction

Abstract

This paper reports a simple, accurate, reproducible, stability-indicating procedure which may be used to quantitatively determine methenamine base, methenamine mandelate or methenamine hippurate in tablet dosage forms. The procedure initially involves the separation of methenamine from the dosage form and from formaldehyde, the decomposition product, by a cartridge ion-pair extraction process. The methenamine may then be assayed by a number of methods. In this paper the methenamine was hydrolyzed to formaldehyde and the formaldehyde determined by the Nash procedure. The method compares favorably with the USP XXI procedure for methenamine tablets. Advantages of the procedure include the ability to use a single method for the base and salt forms of the drug and the potential application to stability and quality control studies of methenamine dosage forms.