The medulla and papilla are the target sites for phenylbutazone, the tubules are targets for many plant toxins, the loop of Henle is the target site for fluoride, and the glomeruli for immune complexes. The elimination or disappearance(by metabolic change) of a chemical from an organ or the body is expressed in terms of half life(th), defined as the amount of time required for the disappearance of half of the compound.