Complex sentence: While simple local anesthetics could be used, such medications can show up in drug tests, while grain alcohol acts locally and degrades the myelin sheaths of the nerves so that the horse cannot move its tail.
Split into simpler sentences: While simple local anesthetics could be used, such medications can show up in drug tests. Conversely, grain alcohol acts locally and degrades the myelin sheaths of the nerves so that the horse cannot move its tail.