Estradiol benzoate/progesterone

Estradiol benzoate/progesterone (EB/P4), sold under the brand names Duogynon and Sistocyclin among others, is a combination medication of estradiol benzoate (EB), an estrogen, and progesterone (P4), a progestogen. It has been formulated both as short-acting oil solutions and long-acting microcrystalline aqueous suspensions and is given by injection into muscle either once or continuously at regular intervals.

EB/P4 was one of the first combined estrogen and progestogen medications to be introduced for medical use. It was first marketed in Germany as an oil solution in 1950. Microcrystalline EB/P4 in aqueous suspension was developed and marketed under the brand name Sistocyclin several years later. EB/P4 was eventually superseded by longer-acting parenteral estrogen–progestogen combinations as well as by oral estrogen–progestogen combinations.