What is Estring (estradiol) used for in menopausal women?

What is Estring (Estradiol Vaginal Ring)?

Estring is a low-dose estradiol-releasing silicone vaginal ring specifically designed to treat moderate to severe symptoms of vulvar and vaginal atrophy (vaginal dryness, itching, burning, and painful intercourse) in postmenopausal women. 1, 2

Mechanism and Delivery System

Estring releases 6.5 to 9.5 micrograms of estradiol per 24 hours continuously over a 3-month period, providing local vaginal estrogen therapy with minimal systemic absorption. 3 The ring is inserted into the vagina and replaced every 3 months, offering a convenient alternative to daily creams or tablets. 4, 3

Primary Indications

Estring is FDA-approved for treating moderate to severe symptoms of vulvar and vaginal atrophy associated with menopause, particularly when topical vaginal products are preferred over systemic hormone therapy. 2 The specific symptoms it addresses include:

• Vaginal dryness and discomfort 1, 4
• Itching and burning sensation 1
• Painful intercourse (dyspareunia) 1, 5
• Vaginal irritation 1

Clinical Efficacy

Estring demonstrates approximately 90% responder rates for both subjective symptoms and objective signs of vaginal mucosal atrophy, with effects maintained throughout 1 year of continuous use. 3 The ring effectively restores vaginal pH to normal premenopausal levels (< 5.5) and increases vaginal maturation values, indicating restoration of healthy vaginal epithelium. 3

When compared head-to-head with estriol vaginal cream, Estring showed equivalent efficacy in alleviating vaginal dryness and atrophy signs, but demonstrated superior patient preference. 4

Advantages Over Other Formulations

• Convenience: The ring requires replacement only every 3 months, compared to daily or twice-weekly applications required for creams and tablets 3
• Patient satisfaction: 78% of women used four consecutive rings continuously up to 1 year, and approximately 90% did not remove the ring during 3-month treatment periods 3
• Strong preference: Women with previous experience of other vaginal estrogen forms showed statistically significant preference (p < 0.001) for the ring over creams or tablets 3
• Minimal systemic absorption: The low-dose continuous release minimizes systemic estrogen exposure while maintaining local efficacy 1, 3

Safety Profile

Estring has a favorable safety profile with low discontinuation rates. 3 In a 1-year study, only 6% of women withdrew due to adverse events, with the most common being vaginal irritation (7%) and rare instances of vaginal bleeding (3 women, none associated with malignancy). 3

Important safety consideration: Vaginal estrogen should NOT be used as first-line therapy in women with hormone-sensitive cancers (particularly breast cancer), undiagnosed vaginal bleeding, active liver disease, or recent thromboembolic events. 1, 2

Treatment Algorithm Position

For postmenopausal women with moderate to severe vaginal atrophy symptoms who have failed non-hormonal options (moisturizers and lubricants), low-dose vaginal estrogen like Estring represents the most effective treatment option. 1 The stepwise approach recommended by guidelines is:

1. First-line: Regular vaginal moisturizers (3-5 times weekly) and water-based lubricants during sexual activity 1
2. Second-line: Low-dose vaginal estrogen (Estring, tablets, or creams) when non-hormonal options fail 1
3. Adjunctive therapies: Pelvic floor physical therapy and vaginal dilators for specific indications 1

Special Populations

For breast cancer survivors: Non-hormonal options should be exhausted first. If vaginal estrogen is considered necessary, estriol-containing preparations may be preferable over estradiol formulations, particularly in women on aromatase inhibitors, as estriol is a weaker estrogen that cannot be converted to estradiol. 1 However, this decision requires thorough discussion of risks and benefits with the oncology team. 1

Common Pitfalls to Avoid

• Do not prescribe Estring for prevention of chronic conditions (cardiovascular disease, osteoporosis, dementia) - it is contraindicated for this purpose and increases risks of stroke, blood clots, and other serious adverse events 6
• Do not use systemic hormone therapy when local vaginal symptoms are the only indication - topical vaginal products like Estring should be considered first 2
• Do not assume all vaginal estrogen formulations have identical systemic absorption - vaginal estradiol tablets and rings may increase circulating estradiol levels differently, particularly relevant in aromatase inhibitor users 1