Beakers and vials with colored liquid

What is botulinum toxin?

Botulinum toxin is a neurotoxin derived from the bacteria Clostridium botulinum. While there are 8 types of botulinum toxin (types A through H), only 2 types are used in humans and sold commercially and medically.

Botulinum toxin A vs B

You will learn:

  • Type A – Botulinum toxin type A, when injected into muscles, blocks neurotransmitters from sending signals between the brain and the nerve, effectively preventing muscle contractions from occurring. Type A is available sold for cosmetic and medical uses under the brands Botox, Dysport, and Xeomin. Botox and Dysport are both provided in powder form and require reconstitution using saline solution prior to injection at a doctor’s office.
  • Type B – Botulinum toxin type B functions in the same capacity as type A. There is currently only 1 product on the market for human use containing type B, Myobloc. Myobloc, also known as Neurobloc, is only indicated for medical use to treat cervical dystonia, a painful condition wherein neck muscles contract uncontrollably, and is not currently approved for cosmetic applications. It is provided as a clear, colorless to yellow solution that may be diluted at a doctor’s office depending on the area being treated and the recommended dosage.


The method of injection for each type of botulinum toxin is as follows:

  • Type A – After reconstituting the powder using a saline solution, inject the solution intramuscularly into the muscles causing the issue being treated (whether medical or cosmetic in nature). Typically, a needle between the sizes of 27G to 30G should be used. Injections should not be performed any more frequently than every 3 months.
  • Type B – Depending on dosage and the areas being treated, the solution may be diluted using sodium chloride. The solution should be injected intramuscularly into the affected areas, and patients should receive injections no more frequently than 3 months apart.

Mechanism of action

Botulinum toxin type A and B both have the same mechanism of action. Upon injection, the toxin attaches itself to nerves that use acetylcholine, a neurotransmitter, and then is transported into the vesicle. Upon moving further into the cell the vesicle acidifies, which triggers the toxin to push across the vesicle membrane and into the cytoplasm. Once there, the toxin cleaves to SNARE proteins, thus preventing the release of vesicles of the neurotransmitter. This effectively prevents all signaling from the nerve, leading to paralysis of the muscles in which the toxin was injected.

Side effects

Though botulinum toxin type A and B both have a proven safety profile and are approved by regulating medical bodies for safe use, side effects may appear following injection with either type.

  • Type A – In addition to side effects associated with injection, such as pain, swelling, redness, and bruising at the injection site, botulinum toxin type A can produce reactions in the body that are less localized. Drooping eyelids and headaches are 2 of the most common side effects, while flu-like symptoms, nausea, reduced blinking, and weakness of the muscles surrounding the treated area may also occur. In very rare cases, the toxin may spread further into the body than it was intended, which can lead to problems swallowing, speaking, and breathing. If these rare reactions occur, patients should immediately seek medical assistance. All of these reactions may occur within in hours of injection, or up to weeks after treatment. 
  • Type B – Common side effects of treatment may include muscle weakness near the injection site, headache, pain or stiffness in the neck or back, dizziness, drowsiness, dry mouth, nausea, fever of fly-like symptoms. Rarely, patients may experience unusual or severe muscle weakness in areas other than the treatment site, loss of bladder control, chest pain, vision issues, and trouble breathing, speaking, and swallowing. If these rare reactions occur, the patient should immediately seek medical assistance. Similar to type A, side effects can occur within hours or up to weeks after injection.


While each brand is made of similar material, they have different ids and slightly different formulations.

  • Type A – Botox is measured in Allergan units and in addition to botulinum toxin, it is formulated with human albumin and sodium chloride. Dysport is also formulated with human albumin, as well as lactose. Xeomin is formulated with human albumin and sucrose.
  • Type B – In addition to botulinum toxin, Myobloc contains human serum albumin, sodium succinate, and sodium chloride.

Antibody test

Though not common, it is believed that some patients, upon repetition injections, may develop antibodies against botulinum toxin. This antibody results in injections becoming less effective.

  • Type A – The test for determining whether a patient has developed antibodies for botulinum toxin type A is called the extensor digitorum brevis (EDB) test. This test has a sensitivity of 80% and a specificity of 94%. If it is determined that a patient has developed the antibody to botulinum toxin type A, they may wish to switch to receiving injections of botulinum toxin type B.
  • Type B – ELISA-based evaluations can be used to determine whether patients have developed antibody responses to botulinum toxin type B and then can receive further testing to be sure.


There is a difference between the prices of each product, and even the price of the same product can vary depending on the areas being treated and location in which the injections are taking place.

  • Type A – Botox injections can cost anywhere between $300 and $1,000, while Dysport is less expensive at about $300 to $400 for injections. However, Dysport contains a lower concentration of botulinum toxin and may require more injections before seeing results. Xeomin is somewhere between Botox and Dysport in terms of price, costing anywhere between $400 and $600.
  • Type B – The average price of Myobloc is approximately $310 for a vial of 0.5 milliliters, which is approximately 2,500 units of botulinum toxin, depending on the pharmacy it is being purchased at.

In what form is botulinum toxin type A administered?

Botulinum toxin type A is administered in a reconstitution liquid solution. This liquid should be clear, colorless, and free of particulate matter, and it should not be injected if it does not meet these criteria.

In what form is botulinum toxin type B administered?

Botulinum toxin type B is administered as a liquid. It should be clear and colorless to light yellow solution and should not be injected if it does not meet these criteria.


Though there are many similarities between botulinum toxin type A and type B, it is important to remember that the things that make them distinct are very important. Chiefly, it is important to remember that they are different and their dosage is neither comparable nor interchangeable with either type or any other botulinum toxin product.
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Disclaimer: These articles, and any views and opinions expressed, are not endorsed by Raskel Medical. The articles are strictly for informational purposes and should not be considered medical advice. Raskel Medical does not check or edit the content of these articles for medical accuracy. Contact your medical practitioner for any medical advice needed.