Continuing medical educationInjectable and topical neurotoxins in dermatology: Basic science, anatomy, and therapeutic agents
Section snippets
History
In the early to mid-1800s, “sausage poison,” now known as botulism, was a major and lethal source of food poisoning in Europe.1 In 1989, after much investigation and scientific research, Clostridium botulinum's bacterial toxin was approved for a variety of medical uses, including hemifacial spasms, strabismus, and blepharospasm.1 A serendipitous discovery by ophthalmologist Jean Carruthers in the late 1980s recognized reduced facial wrinkles in patients with benign essential blepharospasm who
Basic science
Key points Botulinum toxin has 7 serotypes purified from the anaerobic, Gram-positive, spore-forming Clostridium botulinum Botulinum toxins are 150-kDa proteins that are distinguished by the variations in their light chains Incobotulinumtoxin is free from complexing proteins The mechanism of action involves toxin cleavage of the SNARE protein complex with resultant dysfunction of acetylcholine release at the neuromuscular junction
Seven serotypes (A through G) of botulinum toxin have been identified and
Overview of commercially available formulations approved by the FDA
Key points There are 4 commercially available formulations of botulinum toxin in the United States: onabotulinumtoxin, incobotulinumtoxin, abobotulinumtoxin, and rimabotulinumtoxin Each formulation has unique properties, and the neuromodulators are not interchangeable Incobotulinumtoxin is unique in its stability at room temperature storage Reconstitution with bacteriostatic saline reduces injection discomfort Diffusion is suggested to be multifactorial; however, abobotulinumtoxin generally features larger
Future toxins
Key points A peptide was developed that enables transcutaneous flux of toxin, allowing for a topical formulation on the horizon RT002 is a new injectable agent with limited diffusion and longer duration of effect Various formulations are available overseas
Anatomy
Key points Appreciating the contraction patterns and the 3-dimensionality of the facial muscles is critical to safe and effective injection There are anatomic variations based upon age, location, and sex that must be taken into consideration A complete understanding of muscle function and position is crucial to avoid adverse events
All superficial facial muscles work together to form the superficial musculoaponeurotic system, which allows for the fluidity of facial movements. Generally, hyperfunctional lines
Summary
C botulinum is an anaerobic, spore-forming bacterium whose toxin has been purified and exploited for both therapeutic and cosmetic uses. Onabotulinum, abobotulinum, and incobotulinum represent the 3 most commonly used formulations within the United States, each exerting effects on the presynaptic terminal to cause neuromuscular blockade and clinically evident muscle relaxation. Physicians embarking on the use of neurotoxins for cosmetic purposes must have a complete understanding of the
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Funding sources: None.
Conflicts of interest: None declared.
Reprints not available from the authors.
Date of release: June 2017
Expiration date: June 2020