Estradiol (medication)
Estradiol is available in a variety of different formulations, including oral, intranasal, transdermal/topical, vaginal, injectable, and implantable preparations. An ester may be attached to one or both of the hydroxyl groups of estradiol to improve its oral bioavailability and/or duration of action with injection. Such modifications give rise to forms such as estradiol acetate (oral and vaginal), estradiol valerate (oral and injectable), estradiol cypionate (injectable), estradiol benzoate (injectable), estradiol undecylate (injectable), and polyestradiol phosphate (injectable; a polymerized ester of estradiol), which are all prodrugs of estradiol.
Estradiol cypionate
Estradiol cypionate is and has been available as an oil solution for intramuscular injection provided in vials and ampoules at concentrations of 1, 3, and 5 mg/mL (and containing 5, 10, 15, 25, or 50 mg estradiol cypionate total). The 1 and 3 mg/mL concentrations (containing 5 and 15 mg estradiol cypionate total) have been discontinued in the United States, but the 5 mg/mL concentration (containing 25 mg estradiol cypionate total) remains available. Aside from estradiol cypionate, the only other injectable estrogen formulations that remain available in the United States are estradiol valerate (10 mg/mL, 20 mg/mL, and 40 mg/mL in oil) and conjugated estrogens (25 mg/vial in solution).