The need for adequate means by which to improve urine output is very old. Even in the "Scuola Salernitana," the oldest medieval medical school in Western Europe, about 1000 years ago it was taught how to improve urine output. The list of known "diuretica" included herbs, plants, roots, vegetables, in particular asparagus, fennel and carrot. The first diuretic drugs, however, were mercurial compounds. Thus, calomel, mercurous chloride, was initially used as a diuretic in the sixteenth century by Paracelsus, being one of the ingredients of the so-called "Guy's Hospital pill." But calomel had a...