FREDERICK J. AI,LAN' AND G. GR-11-IAM ALLAN' ... More than three-quarters of a century has elapsed since antipyrine (Ia) was introduced into medicine by Knorr as an antipyretic and analgesic (1). Altllough pyrazolone anal- gesics have now virtually vanished from the scene in North America and the Scandinavian countries (2), they are still widely used in other areas and considerable efforts have been expended to improve their pharmacological ...