Oligomeric oestradiol esters: a new class of long-acting oestrogens

Dimeric and trimeric oestradiol derivatives were administered as single subcutaneous injections into ovariectomized rats and the duration of oestrogenic effect was determined by means of daily vaginal smears. It could be shown that these preparations have a very protracted oestrogenic effect, and their threshold dose is considerably higher as compared to monomeric oestradiol diacetate. A dimeric compound containing one free hydroxy group caused a relatively even response in all animals with a linear relationship between the logarithm of dose and the duration of action. The effect was even more protracted when fully esterified dimeric or trimeric oestradiol succinates were used, but occurred in a more scattering manner. The duration of effect of 40 mug of the trimeric compound exceeded that of the equivalent dose of oestradiol undecylate. It is conceivable that the depot-effect of these oestradiol derivatives is due to delayed elimination.