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. 
The mean oral bioavailability of finasteride is approximately 65%.  Its volume of distribution is 76 L/kg.  The plasma protein binding of finasteride is 90%.  The drug has been found to cross the blood–brain barrier , whereas levels in semen were found to be undetectable.  Finasteride is extensively metabolized in the liver , first by hydroxylation via CYP3A4 and then by aldehyde dehydrogenase .  The metabolites of finasteride have about 20% of its potency in inhibiting 5α-reductase and hence its metabolites are not particularly active.  The drug has a terminal half-life of 5 to 6 hours in adult men (18–60 years of age) and a terminal half-life of 8 hours or more in elderly men (greater than 70 years of age).  It is eliminated as its metabolites 57% in the feces and 40% in the urine .