Prescriptions for Estrogen Replacement Therapy in Ontario Before and After Publication of the Women's Health Initiative Study

To the Editor: Landmark clinical trials can influence prescribing behavior.^1-3 We examined patterns of prescriptions for estrogen replacement therapy (ERT) before and after publication of the Women's Health Initiative (WHI) study⁴ on July 17, 2002. We also examined trends around the publication of the Heart and Estrogen/progestin Replacement Study (HERS)⁵ in 1998.