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. 
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It is extremely toxic to bees. An . Environmental Protection Agency (EPA) study found that micrograms was enough to kill honey bees .  It is also extremely toxic to aquatic life with a study showing concentrations of ppb killing mysid shrimp.  It has increased risk of liver cancer in rats and mice in long term exposure.  It is capable of killing mosquitoes ,  although remains poisonous to cats and dogs, with seizures and deaths being reported due to poisoning.  Specific data on concentrations or exposure is lacking.