FDA’s proposal to withdraw conjugated estrogens ANDAs
Executive Summary
In a May 11 letter to FDA, Zenith asks for data and information relied upon in FDA's Feb. 13 notice of opportunity for a hearing proposing to withdraw the ANDAs. Zenith's requests include the plasma studies submitted by several generic companies seeking "AB" ratings for its conjugated estrogens, the "pharmacokinetic model developed by Wyeth-Ayerst to predict that the rate of absorption of all estrogen sulfates contributes to the proportion of active moeties in the plasma," and the data filed by Wyeth-Ayerst to support the effectiveness of its Premarin (innovator conjugated estrogens) tablets for osteoporosis.