Continuing medical education
Injectable and topical neurotoxins in dermatology: Basic science, anatomy, and therapeutic agents

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Botulinum toxin is a potentially deadly anaerobic bacterial toxin that acts by inhibiting release of acetylcholine at the neuromuscular junction, thereby inhibiting contraction of the exposed striated muscle. There are currently 4 botulinum toxin preparations approved by the US Food and Drug Administration (FDA): onabotulinumtoxin, abobotulinumtoxin, incobotulinumtoxin and rimabotulinumtoxin. While significant overlap exists, each product has unique properties and specifications, including dosing, diffusion, and storage. Extensive physician knowledge of facial anatomy, coupled with key differences of the various neurotoxin types, is essential for safe and successful treatments. The first article in this continuing medical education series reviews key characteristics of each neurotoxin, including new and upcoming agents, and provides an anatomic overview of the most commonly injected cosmetic sites.

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

  1. Botulinum toxin has 7 serotypes purified from the anaerobic, Gram-positive, spore-forming Clostridium botulinum

  2. Botulinum toxins are 150-kDa proteins that are distinguished by the variations in their light chains

  3. Incobotulinumtoxin is free from complexing proteins

  4. 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

  1. There are 4 commercially available formulations of botulinum toxin in the United States: onabotulinumtoxin, incobotulinumtoxin, abobotulinumtoxin, and rimabotulinumtoxin

  2. Each formulation has unique properties, and the neuromodulators are not interchangeable

  3. Incobotulinumtoxin is unique in its stability at room temperature storage

  4. Reconstitution with bacteriostatic saline reduces injection discomfort

  5. Diffusion is suggested to be multifactorial; however, abobotulinumtoxin generally features larger

Future toxins

Key points

  1. A peptide was developed that enables transcutaneous flux of toxin, allowing for a topical formulation on the horizon

  2. RT002 is a new injectable agent with limited diffusion and longer duration of effect

  3. Various formulations are available overseas

Anatomy

Key points

  1. Appreciating the contraction patterns and the 3-dimensionality of the facial muscles is critical to safe and effective injection

  2. There are anatomic variations based upon age, location, and sex that must be taken into consideration

  3. 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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  • Cited by (0)

    Funding sources: None.

    Conflicts of interest: None declared.

    Reprints not available from the authors.

    Date of release: June 2017

    Expiration date: June 2020

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