Which medications in the drug class Neuromuscular Blocker Agent, Toxin are used in the treatment of Lichen Simplex Chronicus?

Updated: Feb 15, 2019
  • Author: Jason Schoenfeld, MD; Chief Editor: William D James, MD  more...
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Answer

Neuromuscular Blocker Agent, Toxin

OnabotulinumtoxinA (BOTOX®)

OnabotulinumtoxinA is one of several toxins produced by Clostridium botulinum. It blocks neuromuscular transmission through a 3-step process, as follows: (1) blockade of neuromuscular transmission; botulinum toxin type A (BTA) binds to the motor nerve terminal. The binding domain of the type A molecule appears to be the heavy chain, which is selective for cholinergic nerve terminals. (2) BTA is internalized via receptor-mediated endocytosis, a process in which the plasma membrane of the nerve cell invaginates around the toxin-receptor complex, forming a toxin-containing vesicle inside the nerve terminal. After internalization, the light chain of the toxin molecule, which has been demonstrated to contain the transmission-blocking domain, is released into the cytoplasm of the nerve terminal. (3) BTA blocks acetylcholine release by cleaving SNAP-25, a cytoplasmic protein that is located on the cell membrane and that is required for the release of this transmitter. The affected terminals are inhibited from stimulating muscle contraction. The toxin does not affect the synthesis or storage of acetylcholine or conduction of electrical signals along the nerve fiber. It prevents calcium-dependent release of acetylcholine and produces a state of denervation at the neuromuscular junction and postganglionic sympathetic cholinergic nerves in the sweat glands.

Typically, a 24- to 72-hour delay between administration of toxin and onset of clinical effects exists, which terminate in 2-6 months.

This purified neurotoxin complex is a vacuum-dried form of purified BTA, which contains 5 ng of neurotoxin complex protein per 100 U.

BTA has to be reconstituted with 2 mL of 0.9% sodium chloride diluent. With this solution, each 0.1 mL results in 5-U dose. The patient should receive 5-10 injections per visit.

OnabotulinumtoxinA must be reconstituted from vacuum-dried toxin into 0.9% sterile saline without preservative using the manufacturer's instructions to provide injection volume of 0.1 mL; it must be used within 4 hours of storage in the refrigerator at 2-8°C.

Preconstituted dry powder must be stored in the freezer at colder than 5°C.

Injections of BTA must be repeated at varying intervals to maintain long-term results.


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