[Mode of action and effects of botulinum neurotoxin A]

Intramuscular injection of botulinum neurotoxin A produces transitory blockade of neuromuscular transmission and inhibits presynaptic release of acetylcholine. Its action affects peripheral cholinergic receptors, which unlike central receptors, can render the toxin active by an internalization mechanism. The intracellular target of botulinum neurotoxin A is a protein of the acetylcholine vesicle membrane. Currently, indications of botulinum neurotoxin A are reserved solely for dystonia. Such treatment has been shown to be effective and tolerance is good; histological modifications (muscle atrophy, denervation and axonal sprouts) have been observed. The most frequently reported side effects are related to high doses and repeated injections of botulinum neurotoxin A.