Short answer: Both put low-dose estradiol in the vagina for menopausal vaginal atrophy. Estring is a soft ring that stays in for 90 days, releasing about 7.5 mcg a day.1 Vagifem is a 10 mcg insert used daily for 2 weeks, then twice a week.2 The Vagifem label carries the estrogen boxed warning; this Estring label version has none. Neither label compares the two.
| Estring | Vagifem | |
|---|---|---|
| Form | Soft ring with 2 mg estradiol, about 7.5 mcg released a day1 | 10 mcg insert in a single-use applicator2 |
| Schedule | Left in continuously for 3 months, then replaced if needed1 | Daily for 2 weeks, then twice a week, for example Tuesday and Friday2 |
| Compared with | Conjugated estrogens vaginal cream1 | Placebo, over 12 months2 |
| Common side effects | Headache 13% vs 16% on the cream; vaginal discharge 7% vs 3%1 | Vaginal yeast infection 8% vs 3% on placebo; itching 8% vs 2%; back pain 7% vs 2%2 |
| Device problems | Ring may slip or fall out; rare toxic shock, sticking to the vaginal wall, erosion1 | Rare scraping from the applicator2 |
| Missed dose | No daily dose; if the ring falls out, rinse and reinsert1 | No rule in the label2 |
| Boxed warning | None in this label version1 | WARNING: ENDOMETRIAL CANCER, CARDIOVASCULAR DISORDERS, PROBABLE DEMENTIA, and BREAST CANCER2 |
Both labels say some estradiol is absorbed into the body. The Vagifem label says the warnings for systemic estrogen apply; the Estring label says how much they apply is not known.21 Vagifem's boxed warning lists endometrial cancer, stroke and clots, probable dementia and breast cancer from the Women's Health Initiative studies of oral conjugated estrogens.2 The Estring label lists endometrial cancer and the same systemic risks under its warnings.1
In Estring's U.S. study, endometrial overstimulation was found in 0 of 58 women on the ring vs 4 of 35 on the cream.1 In Vagifem's 12-month trial, biopsies found one endometrial cancer and one hyperplasia among 172 women.2 These numbers come from separate trials with different people, lengths and methods, so they are not a head-to-head comparison.
Which, if either, fits is for your prescriber. More detail: Estring side effects, Vagifem side effects, the Estring and Vagifem dosing schedules, the vaginal estradiol guide, and Estring vs Femring: how do the two estrogen vaginal rings differ?.