SummaryThe therapeutic action of 16-formylgitoxine has been evaluated in 33 patients. Four of these patients suffered from paroxystic tachycardia; all others were in congestive heart failure with sinusal rhythm in 17, atrial fibrillation in 10 and permanent flutter in 2.Conclusions drawn from the present studies are as follows:1. 16-formylgitoxine is a highly potent cardiotonic drug. The amount required for full digitalization per os averaged 2 to 3 mg given over a period of 3 to 4 days. The maintenance dosage ranged from 0.1 to 0.4 mg daily per os, which is slightly more than when digitoxin is used, but less than in case of use of digoxin or lanatoside C.2. Conversion of a permanent flutter into atrial fibrillation was achieved with 4 to IO mg 16-formylgitoxine given over 7 to 10 days.3. One mg 16-formylgitoxine injected intravenously exerts a near maximal effect in less than 40 minutes, which makes it comparable to digoxine or lanatoside C. The latter two drugs may thus be replaced by 16-formylgitoxine for emergency treatment of cardiac failure associated with tachyarrhythmia or of paroxystic tachycardias (auricular fibrillation, flutter, supraventricular tachycardia). In such cases, 1 mg should be given intravenously, and again one hour later if need be.4. The amount of drug required for full digitalization is 1.0 to 2 mg administered intravenously.5. Only 3 patients, out of 33, complained of gastric intolerance; this side effect is thus less frequently encountered than when digitoxine is prescribed.6. 16-formylgitoxine has a marked diuretic action, to be ascribed to hemodynamic changes rather than to a direct renal influence of the glycoside, since the drug failed to induce a diuresis in a case of constrictive pericarditis.