Among the testosterone derivatives, and in no particular order, levonorgestrel , norgestrel , norgestrienone , ethisterone ,  gestrinone ,  danazol ,  tibolone ,   normethandrone ,  and norvinisterone  have the greatest androgenic activity,      while norethisterone and its prodrugs ( norethisterone acetate , norethisterone enanthate , lynestrenol , etynodiol diacetate , and quingestanol acetate )  have moderate activity.     Testosterone derivatives with low (but potentially still significant) androgenic activity include desogestrel , etonogestrel , gestodene , and norgestimate ,    while norelgestromin ,  noretynodrel ,    norgesterone ,  allylestrenol ,  and dimethisterone  appear to have negligible activity. Dienogest and oxendolone are unique among the testosterone derivatives in that they are potent antiandrogens.  
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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