Valentino

This is an interlocutory appeal from a district court order under Fed.R.Civ.P. 23 conditionally certifying a nationwide plaintiff class and subclass in a products liability case against the manufacturer of a drug used for the treatment of epilepsy. The jurisdiction of the district court was grounded on diversity, and our jurisdiction is pursuant to certification under 28 U.S.C. § 1292 (b).

The drug in question, known as Felbatol, is manufactured by defendants Carter-Wallace, Inc. and Wallace Laboratories (Carter-Wallace). Carter-Wallace began marketing the drug in August 1993 without giving any special warning of serious side effects. Between January 1994 and July 1994, Carter-Wallace received reports that some patients had developed aplastic anemia following use of the *1229 drug. 1 In August 1994, Carter-Wallaee mailed letters to the physician community warning them of this risk. By September 1994, Carter-Wallaee had also received reports of liver failure in connection with use of the drug. Again, Carter-Wallaee mailed letters to the physician community warning them of this risk.

The district court determined that the prerequisites of Fed.R.Civ.P. 23(a) had been met. 2 The…