Valproic acid , and its derivatives such as sodium valproate and divalproex sodium , causes cognitive deficit in the child, with an increased dose causing decreased intelligence quotient .  On the other hand, evidence is conflicting for carbamazepine regarding any increased risk of congenital physical anomalies or neurodevelopmental disorders by intrauterine exposure.  Similarly, children exposed lamotrigine or phenytoin in the womb do not seem to differ in their skills compared to those who were exposed to carbamazepine. 
Ludwig Knorr was a student of Emil Fischer who won the Nobel Prize for his work on purines and sugars, which included the discovery of phenylhydrazine .   In the 1880s, Knorr was trying to make quinolone derivatives from phenylhydrazine, and instead made a pyrazole derivative, which after a methylation, he made into phenazone , also called antipyrine, which has been called "the 'mother' of all modern antipyretic analgesics."   :26–27 Sales of that drug exploded, and in the 1890s chemists at Teerfarbenfabrik Meister, Lucius & Co. (a precursor of Hoechst AG which is now Sanofi ), made another derivative called pyramidon which was three times more active than antipyrine.