HAYWARD, Calif. (AP) — Impax Laboratories Inc. said Wednesday it received FDA approval for a 500-milligram version of the seizure drug Depakote ER. Abbott Laboratories makes Depakote ER, which is used as a treatment for epilepsy and bipolar disorders. The company already received approval for the 250-milligram version in May. Abbott Laboratories makes Depakote and Mylan Inc. already has a generic version on the market. Abbott reported an 80 percent drop in U.S. Depakote sales to $80 million during the second quarter, mainly because of generic competition.