Diuretics have been empirically developed. Inorganic mercury was used as diuretics from 16C. Guy's Hospital Pills (containing the equal part of Hg2Cl2, digitalis, and squill) was well known in the 19 C. Discovery of the diuresis of merbaphen has led to develop many organomercurial diuretics and to give suggestion of the drug design of ethacrynic acid. Diuresis in patients given sulfonamide was discovered in 1938. Inhibition of carbonic anhydrase by sulfonamide was related to its diuresis. Drug design aimed to enhance the inhibition of this enzyme has obtained acetazolamide, then chlorothazide. But, the discovery of remarkably enhanced diuretic activity (decreased inhibition on the enzyme) of hydrochlorothazide changed this drug design to rondom chemical modification of thiazide ring. Then, furosemide and other loop diuretics were obtained. The sturcture-activity relationship of thiazides using the electronic state and other physico-chemical indices was studied by us. A large hydrophobic center linked to a positive formal charge was assumed to the receptor of thiazide. Binding of thiazide to erythrocyte which gives mild and long acting diuretic property was found by us. Recently, shut down of the tubuloglomerular feedback by loop diuretics was reported. Loop diuretics are metabolized to loss their activity. Therapeutic drug monitoring is necessary to obtain a desirable diuresis. By wide clinical use of thiazides and loop diuretics, patients with hyponatremia with eu-or hypervolemic increased. I have proposed aquaretics since 1976. In 1992, nonpeptide selective vasopressin V2 receptor antagonist (OPC-31260) was first synthesized in Japan. This has been found to cause hypotonic diuresis and elevation of serum Na level in men. The combined use of loop diuretics and aquaretics should be considered.
