Description: Amifampridine is used as a drug, predominantly in the treatment of a number of rare muscle diseases. The phosphate salt of amifampridine is a more stable formulation that does not require refrigeration. In the United States, amifampridine is under investigation for the treatment of Lambert-Eaton myasthenic syndrome (LEMS). Amifampridine is also used to treat many of the congenital myasthenic syndromes, particularly those with defects in choline acetyltransferase, downstream kinase 7, and those where any kind of defect causes "fast channel" behaviour of the acetylcholine receptor