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. 
Cetirizine is eliminated approximately 70 to 85% in the urine and 10 to 13% in the feces .  About 50 or 60% of cetirizine eliminated in the urine is unchanged.   It is eliminated in the urine via an active transport mechanism.  The elimination half-life of cetirizine ranges from to 10 hours in healthy adults, with a mean across studies of approximately hours.   Its duration of action is at least 24 hours.  The elimination half-life of cetirizine is increased in the elderly (to 12 hours), in hepatic impairment (to 14 hours), and in renal impairment (to 20 hours).