Serum concentrations of estriol vary widely after application of vaginal oestriol cream.

Postmenopausal E3 concentrations are negligible. Serum E3 concentrations of chronic users of E3 cream varied greatly; however, concentrations declined rapidly within 8 h, generally reaching 'postmenopausal' levels by 24 h. The basis for the variation between subjects needs further elucidation. Additional research is required to establish the safety of topical E3 .