Chemically, glyceryl behenate is a mixture of various esters of behenic acid and glycerol (glycerides). An ester interchange of that product with glycerol leads to the glyceryl ester. Glycerol acts as a catalyst, as the reaction proceeds through a glyceryl oxalate intermediate. Agents include nitroglycerin (glyceryl trinitrate) or pentaerythritol tetranitrate, isosorbide dinitrate and isosorbide mononitrate. The glyceryl ester of clonixin, clonixeril, is also a NSAID. Glyceryl diacetate is a food additive with the E number E1517. It is usually used for medications such as glyceryl trinitrate, for example, in angina pectoris. This led to the development of transdermal patches of glyceryl trinitrate, providing 24-hour release. Glyceryl behenate is a fat used in cosmetics, foods, and oral pharmaceutical formulations. Currently, guaifenesin (glyceryl guaiacolate) is the only FDA approved expectorant in the United States. The mixture predominantly contains the diester glyceryl dibehenate. Thus, glyceryl trinitrate works best when used only in short-term, pulse dosing. Glyceryl hydroxystearate is an ingredient found in some personal-care products. The medical establishment also used the name "glyceryl trinitrate" for the same reason. It contains glyceryl trinitrate and is sold in patch form.