Botulinum toxin (BTX) is a neurotoxin produced by the bacterium Clostridium (C.) botulinum, which blocks the release of the neurotransmitter, acetylcholine, at the neuromuscular junction, thereby interfering with nerve transmission and blocking subsequent muscle contraction. BTX is used to reduce excessive muscle contraction or spasm associated with a variety of movement disorders that include spasticity and/or tremors.