Barr & Wyeth Ayerst's Premarin Battle

In the long-running generics battle between Barr Laboratories and Wyeth-Ayerst (Marketletters passim), the latter has received a preliminary analysis of the chemical components of its Premarin (conjugated estrogens), for the treatment of menopause symptoms, from the US Food and Drug Administration.

The FDA has defined three criteria which must be met to determine which components of Premarin are essential to its clinical effects, and therefore must be included in a generic form of the drug. Wyeth has submitted data to the FDA which highlight the importance of the estrogen delta 8,9 DHES, which is currently classified as an impurity, to the compound. The company says that it relieves hot flushes and night sweats, as well as preventing bone loss and having antioxidant properties.

Barr Laboratories is reserving comment on this latest news, but said that it would add the estrogen to its generic product if the FDA so requires.