Complex sentence: Flupirtine was originally developed by Asta Medica, and has been approved in Europe since 1984 for the treatment of pain, however it has never been introduced to the United States market for any indication.
Split into simpler sentences: Flupirtine was originally developed by Asta Medica, and was approved for the treatment of pain in 1984 in Europe. However it has never been introduced to the United States market for any indication.