Estradiol benzoate/hydroxyprogesterone caproate (EB/OHPC), sold under the brand name Primosiston among others, is a combined estrogen and progestogen medication which is used to treat gynecological disorders and habitual abortion. It contains estradiol benzoate (EB), an estrogen, and hydroxyprogesterone caproate (OHPC), a progestin. The medication is given by injection into muscle.
EB/OHPC is used in the treatment of gynecological disorders such as menstrual disorders (e.g., amenorrhea, dysfunctional uterine bleeding) and premenstrual syndrome, habitual abortion (threatened miscarriage), and for other indications.
EB/OHPC is available in the form of ampoules of oil solutions containing 10 mg estradiol benzoate (EB) and 125 to 250 mg hydroxyprogesterone caproate (OHPC).
EB/OHPC was first introduced for medical use in 1955.
EB/OHPC has been marketed under brand names including Dos Dias N, Lutes, Ostrolut, Primosiston (or Primosiston Inj. / Injection), Primosiston Fuerte, and Syngynon.
EB/OHPC has been mostly discontinued and hence is mostly no longer available. It remains marketed under the brand names Primosiston in Ecuador and Peru, Dos Dias N in Argentina, and Lutes in Japan. It was previously marketed under the brand names Ostrolut in Austria; Primosiston (or Primosiston Inj. / Injection) (Schering) in Argentina, Germany, Mexico, Switzerland, and Venezuela; Primosiston Fuerte in Spain; and Syngynon in Germany, but these formulations have all been discontinued and hence are no longer available in these countries.