Since 1933 a number of drugs capable of preventing histamine reactions in animals have been reported. The first of these, 929F (2-thymoloxytriethylamine), was found by Fourneau and Bovet1to be capable of inhibiting or counteracting the action of histamine in guinea pigs. In 1937 Staub and Bovet2confirmed these observations. In 1939 Staub3reported a compound with an ethylenediamine radical, 1571F (N,N,N'-triethylethylenediamine), with similar qualities. These drugs, while exhibiting a decided antihistaminic effect, were toxic and could not be studied in man. In 1942 Halpern4investigated a large number of antihistaminic drugs and found one, 2339 R. P., which could be used in man. This drug, N-phenyl-N-benzyl-N',N'-dimethylethylene diamine, was introduced in France for clinical use under the trade name "antergan." In 1944 a less toxic antihistaminic drug, pyranisamine maleate, known as 2786 R. P. (neo-antergan®), was reported by Bovet, Horclois and Walthert.5In 1945 tw