ATC Group: M03AX Other muscle relaxants, peripherally acting agents

Botulinum toxin type A is a protein complex derived from Clostridium botulinum. The protein consists of type A neurotoxin and several other proteins. Under physiological conditions it is presumed that the complex dissociates and releases the pure neurotoxin. Intramuscular injection of the neurotoxin complex blocks cholinergic transport at the neuromuscular junction by preventing the release of acetylcholine. The nerve endings of the neuromuscular junction no longer respond to nerve impulses and secretion of the chemotransmitter is prevented (chemical denervation).

Botulinum toxin type B is a neuromuscular blocking agent indicated for the treatment of cervical dystonia. When injected directly into a muscle, it causes a localised paralysis that gradually reverses over time.