Hello and Welcome to ‘Ask A Doctor’ service. I have reviewed your query and here is my advice. There are several interaction between Zanaflex and Keppra. Some of the symptoms can be: -Chest pain -blood clot in a major vein that usually develops in the legs and/or pelvis -loss of full control of bodily movements -Fall -headache I suggest you to consult your doctor for further evaluation. Hope I have answered your query. Let me know if I can assist you further.