Drug reference

Conjugated Estrogens (Equine)

Estrogen · Hormone Replacement Therapy

Also known as Conjugated estrogens

EstrogenHormone Replacement Therapy

CDSCO approvedSchedule H

EXCRETION

—

not curated

INTERACTIONS

—

none in our sources

PREGNANCY

—

not curated

Mechanism

Conjugated estrogens act as agonists at estrogen receptors (ERs). Agonist binding to the ligand binding domain brings about receptor dimerization and interaction with estrogen response elements (EREs) of target genes, promoting gene transcription through coactivator proteins. Estradiol binds to both ERα and ERβ with equal affinity.

Indications

Menopausal symptomsPostmenopausal osteoporosis prophylaxisDysfunctional uterine bleeding

Dosing

Adult: Oral for menopausal symptoms: 0.3–1.25 mg daily continuously; with cyclical progestogen for 12–14 days of each cycle in women with a uterus. Oral for postmenopausal osteoporosis prophylaxis: 0.625–1.25 mg daily continuously; with cyclical progestogen for 12–14 days of each cycle in women with a uterus. For dysfunctional uterine bleeding: 25 mg IV or IM.
Max dose: 1.25 mg daily (oral); 25 mg (IV/IM for dysfunctional uterine bleeding)

Pharmacokinetics

Bioavailability

Low absolute oral bioavailability due to first-pass metabolism; undergoes partial presystemic metabolism. Conjugated estrogens are hydrolyzed by enzymes in the lower gut that remove charged sulfate groups, allowing absorption across the intestinal epithelium.

Metabolism

Undergoes first-pass hepatic metabolism and partial presystemic metabolism. Hydrolyzed by enzymes in the lower gut.

Contraindications

Active arterial thromboembolic disease

Side effects

Serious

Increased risk of breast cancer (risk increases with longer duration of use and is higher for combined estrogen-progestogen HRT than estrogen-only HRT)
Active arterial thromboembolic events