Comparative Pharmacology

Estradiol binds to and activates estrogen receptors (ERα and ERβ) in target tissues, modulating gene transcription and non-genomic signaling pathways. Progesterone binds to the progesterone receptor (PR), regulating endometrial differentiation and inhibiting estrogen-induced mitogenesis.

Estradiol 1 mg orally once daily plus progesterone 200 mg orally once daily for 12-14 days per cycle (or continuous combined regimen: estradiol 0.5-1 mg orally once daily plus progesterone 100 mg orally once daily). For hormone replacement therapy: estradiol 0.5-2 mg orally once daily continuously; medroxyprogesterone acetate 2.5-5 mg orally once daily for 12-14 days per month (if progesterone used). Menopausal vasomotor symptoms: estradiol 0.5-1 mg orally once daily; if uterus intact, add progesterone 200 mg orally once daily for 12 days per month or 100 mg orally once daily continuously. Osteoporosis prevention: estradiol 0.5 mg orally once daily; progesterone as above. Topical: estradiol transdermal system 0.025-0.1 mg/day applied once weekly; progesterone vaginal gel 4% or 8% inserted once daily. Dose titrated to minimum effective. Maximum daily estradiol dose: 2 mg orally.