Estradiol (medication)
Estradiol is also available in the U.S. in combination with progestogens for the treatment of menopausal symptoms and as a combined hormonal contraceptive:Estradiol and estradiol esters are also available in custom preparations from compounding pharmacies in the U.S. This includes subcutaneous pellet implants, which are not available in the United States as FDA-approved pharmaceutical drugs. In addition, topical creams that contain estradiol are generally regulated as cosmetics rather than as drugs in the U.S. and hence are also sold over-the-counter and may be purchased without a prescription on the Internet.
Estradiol acetylsalicylate
Estradiol acetylsalicylate, or estradiol 3-acetylsalicylate, is a synthetic estrogen and estrogen ester – specifically, the C3 acetylsalicylic acid (aspirin) ester of estradiol – which was described in the late 1980s and was never marketed. In dogs, the oral bioavailability of estradiol acetylsalicylate was found to be 17-fold higher than that of unmodified estradiol. However, a subsequent study found that the oral bioavailability of estradiol and estradiol acetylsalicylate did not differ in rats (4.3% and 4.2%, respectively), suggestive of a major species difference.