The present invention contemplates a high dose finished pharmaceutical dosage form comprising a methenamine salt, such as methenamine mandelate, as an active pharmaceutical ingredient wherein the methenamine salt API has a moisture content that is less than the upper limit specified in the USP. A preferred embodiment of the present invention has a moisture content that is half of the limit set forth in the USP for each particular methenamine salt. An even more preferred embodiment has a moisture content of less than or equal to one-tenth of a percent (0.1%), regardless of the methenamine salt. The present invention may include one or more pharmaceutically acceptable ingredients. The present invention also contemplates a moisture content of the high dose finished pharmaceutical dosage form that is less than one percent.
