Valproic acid was first synthesized in 1882 by Beverly S. Burton as an analogue of valeric acid , found naturally in valerian .  Valproic acid is a carboxylic acid , a clear liquid at room temperature. For many decades, its only use was in laboratories as a "metabolically inert" solvent for organic compounds. In 1962, the French researcher Pierre Eymard serendipitously discovered the anticonvulsant properties of valproic acid while using it as a vehicle for a number of other compounds that were being screened for antiseizure activity. He found it prevented pentylenetetrazol -induced convulsions in laboratory rats .  It was approved as an antiepileptic drug in 1967 in France and has become the most widely prescribed antiepileptic drug worldwide.  Valproic acid has also been used for migraine prophylaxis and bipolar disorder. 
On April 8, 1997, after buying the remaining % of Roussel-Uclaf stock in early 1997,  Hoechst AG ( US$30 (equivalent to $ in 2017) billion annual revenue) announced the end of its manufacture and sale of Mifegyne ( US$ (equivalent to $ in 2017) million annual revenue) and the transfer of all rights for medical uses of mifepristone outside of the United States to Exelgyn ., a new single-product company immune to antiabortion boycotts, whose CEO was former Roussel-Uclaf CEO Édouard Sakiz.  In 1999, Exelgyn won approval of Mifegyne in 11 additional countries, and in 28 more countries over the following decade.