Letters Section Editor: Robert M. Golub, MD, Senior Editor.
In Reply: Dr Shephard highlights an important difference between low- and high-dose estradiol (E2) vaginal rings. The low-dose, 7.5 μg per day E2-releasing vaginal ring (Estring; Pharmacia & Upjohn, Kalamazoo, Mich) used by the patient in the presentation produces mean steady-state serum E2 levels of 6 to 8 pg/mL.1 This dose is appropriate for the treatment of genital atrophy only as systemic levels are too low to ameliorate vasomotor symptoms. Since endometrial proliferation does not usually occur until serum E2 levels exceed 19 pg/mL,2 the routine addition of a progestin is not recommended during low-dose therapy.3 Higher dose (50 and 100 μg/day) E2-releasing vaginal rings are also available (Femring; Warner Chilcott, Larne, Northern Ireland), which achieve mean daily serum E2 concentrations of 41 to 76 pg/mL—doses sufficient to decrease the number and severity of hot flashes.4 As with any form of systemic estrogen therapy, high-dose E2 vaginal rings should only be used when systemic absorption is the desired outcome, and appropriate precautions regarding endometrial protection should be followed.
Potter JE. Low- vs High-Dose Estradiol Vaginal Ring in Treatment of Sexual Difficulties—Reply. JAMA. 2007;297(19):2076-2077. doi:10.1001/jama.297.19.2076-c