How does Estring work?
Estring is an off-white, flexible ring that releases estradiol into the vagina at a consistent rate for 90 days.
Estrogens are responsible for many functions in the human body, mainly for the development of the female reproductive system and secondary sex characteristics. Estradiol is the principal intracellular estrogen and is much more potent than its metabolites (estrone and estriol). Estradiol is the primary estrogen secreted before menopause, while estrone and estrone sulfate are more highly produced after menopause.
Estrogens modulate the pituitary secretion of gonadotropins, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) through a negative feedback loop. Estrogens act to reduce the elevated levels of these hormones in postmenopausal women.
Dosage and How to Use
Estring is only available as a 2 mg ring.
One Estring should be pressed into an oval and inserted as deeply as possible into the upper one-third of the vaginal vault. If the patient feels discomfort, Estring is probably not far enough inside.
The ring should remain in place for 90 days. The patient should not feel Estring when it is in place, and it should not interfere with sexual intercourse. Straining at defecation may make Estring move down in the lower part of the vagina. If so, it may be pushed up again with a finger.
After 90 days, the ring should be removed and, if indicated, replaced by a new ring. The need to continue treatment should be evaluated every 3 to 6 months.
If the ring falls out at any time during the 90-day treatment period, the ring should be rinsed in lukewarm water and re-inserted by the patient, physician, or nurse.
Retaining the ring for longer than 90 days will not cause overdosage, but it will result in progressively greater under dosage.
Estring can be removed by hooking a finger through the ring and pulling it out.
Store at room temperature 15° to 30° C (59° to 86° F).
Estrogen overdosage may cause nausea, vomiting, breast tenderness, abdominal pain, drowsiness, and withdrawal bleeding (in women). Overdosage treatment consists of removing Estring and appropriate care to reduce symptoms.
The more common side effects of Estring include:
- Breast pain
- Irregular vaginal bleeding or spotting
- Stomach/abdominal cramps, bloating
- Nausea and vomiting
- Hair loss
- Fluid retention
- Vaginal yeast infection
Rare but serious side effects of Estring include:
- Breast cancer
- Cancer of the uterus
- Heart attack
- Blood clots
- Gallbladder disease
- Ovarian cancer
- High blood pressure
- Liver problems
- High blood sugar
- Enlargement of benign tumors of the uterus (“fibroids”)
Warning signs of a serious side effect may be:
- Breast lumps
- Unusual vaginal bleeding
- Dizziness and faintness
- Changes in speech
- Severe headaches
- Chest pain
- Shortness of breath
- Pains in your legs
- Changes in vision
- Yellowing of the skin, eyes, or nail beds
Call your doctor immediately if you experience any of these warning signs or any other unusual symptoms that raise concern.
This is not a comprehensive list of all possible side effects. Please contact your doctor or pharmacist for more information.
Warnings & Precautions
Cardiovascular disorders (stroke, coronary heart disease, and venous thromboembolism)
- The Women’s Health Initiative (WHI) estrogen-alone substudy reported increased risks of stroke and deep vein thrombosis (DVT).
- The WHI estrogen plus progestin substudy reported increased risks of DVT, pulmonary embolism (PE), stroke, and myocardial infarction (MI).
- Do not use estrogen-alone or estrogen plus progestogen therapy for the prevention of cardiovascular disease.
Malignant Neoplasms (endometrial cancer, breast cancer)
- There is an increased risk of endometrial cancer in a woman with a uterus who uses unopposed estrogens.
- The WHI estrogen plus progestin substudy reported increased risks of invasive breast cancer.
- The WHI Memory Study (WHIMS) estrogen-alone ancillary study of WHI reported an increased risk of developing probable dementia in postmenopausal women 65 years and older.
- The WHIMS estrogen plus progestin ancillary study of WHI reported an increased risk of developing probable dementia in postmenopausal women 65 years and older.
- Do not use estrogen-alone or estrogen plus progestogen therapy for the prevention of dementia.
Other Warnings & Precautions
- Gallbladder disease
- Visual Abnormalities
- Addition of a progestin should be strongly considered in women that have not had a hysterectomy
- Elevated blood pressure
- Impaired liver function and history of cholestatic jaundice
- Fluid retention
- Exacerbation of endometriosis
- Exacerbation of other conditions (e.g., diabetes mellitus, epilepsy, migraine)
- Vaginal irritation
- Vaginal infection
Drug Interactions and Other Interactions
Studies have shown that estrogens are metabolized partially by cytochrome P450 3A4 (CYP3A4). Inducers or inhibitors of CYP3A4 may affect estrogen drug metabolism.
CYP3A4 inducers (e.g., St. John’s Wort, phenobarbital, carbamazepine, and rifampin) may reduce plasma concentrations of estrogens.
CYP3A4 inhibitors (e.g., clarithromycin, erythromycin, ketoconazole, itraconazole, ritonavir, grapefruit juice) may increase plasma concentrations of estrogens.
Estring should not be used in women with any of the following:
- Undiagnosed abnormal genital bleeding
- Known, suspected, or history of breast cancer or other estrogen-dependent neoplasia
- Active or history of deep vein thrombosis or pulmonary embolism
- Active or recent (within the past year) arterial thromboembolic disease (for example, stroke and myocardial infarction)
- Known liver dysfunction
- Known hypersensitivity to any of the ingredients in Estring
- Known or suspected pregnancy