Ent-16-amino-17-hydroxy-oestra-1,3,5(10)-trienes and derivatives thereof, and pharmaceutical compositions

New and pharmacologically useful ent-16-amino-17-hydroxy-oestra-1,3,5(10)-trienes are disclosed having the formula I: I and pharmaceutically acceptable non-toxic acid addition salts thereof, wherein: n=1 or 2, preferably 1 R1=H or hydrocarbyl of 1 to 6 carbon atoms (preferably lower alkyl, such as methyl); R2=H or hydrocarbyl of 1 to 6 carbon atoms (preferably lower alkyl, such as methyl); or R1 and R2 together is alkylene of 4 or 5 carbon atoms; R3=a free, esterified or etherified hydroxyl group; and R4=a free, esterified or etherified hydroxyl group. The novel compounds have antiarrhythmic properties.