Botulinum toxin type A and type B are the only two serotypes approved for cosmetic purposes. As you may know, botulinum toxin is a biological agent that has been isolated from the Hall strain of Clostridium bacterium and adapted for cosmetic and clinical use. In addition to their composition, botulinum toxin type A and B differ in the way they are prepared for use thus dilution, injection procedure, their particular mechanism of action, results duration treatment cost and other factors. This article covers some of the most important differences in a quick easy to read format.
If you are running short on time, jump to a simplified table summarizing all information on this article by clicking here.
Differences in Preparation
Botulinum toxin type A (Botox) comes in sterile, vacuum-dried purified form consisting of several accessory proteins, supplied in a single-use vial. The reconstituted solution must be clear, colorless, and free of particulates. Botox is available in 50, 100, and 200 units per vial formulation.
Botulinum toxin type B is manufactured as a purified solution in a ready-to-use vial injected as an intact complex. Dosaging is different from other BT preparations, with a concentration of 5,000units/ml. The equivalent conversion ratio to BT type A is a wide range of 1:125.35.
Injection Procedure Differences
Draw 2.5ml of 0.9% sterile saline without preservative using a 21G needle and appropriately sized syringe. Slowly inject it into the Botox vial at a 45° angle. Gently rotate the vial and record the time and date of reconstitution. For glabellar facial lines, inject a dose of 0.1ml into each of 5 sites using a 30G needle for a total dose of 20 units. Refer to the product pamphlet for other indications.
Patients with prior history of tolerating BT therapy must start with an initial dose of 2,500–5,000 units divided among the affected muscles. Myobloc comes in a ready to use vial and does not require dilution. It can still be diluted with normal saline and the reconstituted solution must be used within 4 hours. Dilution for BT type B is 0.01cc–50 units.
Mechanism of Action Differences
Type A products block the neuromuscular transmission by attaching to the receptor sites on motor neuron terminals, and inhibiting the release of acetylcholine. The inhibition is initiated when the neurotoxin cleaves SNAP-25—a protein essential for the successful release of acetylcholine.
Just like type A, neurotoxin type inhibits the release of acetylcholine at the neuromuscular junction. But type B inhibition occurs by cleaving synaptobrevin or synaptic vesicle associated membrane proteins (VAMP)—an important component of the protein complex that facilitates neurotransmitter release.
The effects of BT type A products are often felt within a few days and may last up to 4 months. Patients who want to maintain the positive results from Botox will need to undergo repeat sessions every 3 to 4 months.
A double-blind randomized study in 2003 showed that BT type B is comparable to type A in rapidly and satisfactory reducing fine lines in the perioral area but has a shorter duration of effects. When used for treating glabellar wrinkles, Myobloc (BT type B) was reported to be safe and effective at a dose of 1,800 units, but the longevity only lasts for 8 weeks. Higher doses tend to result in a longer duration of effect.
Side effects Differences
Adverse events from Type A and Type B injections are almost similar, but studies confirmed that type B is associated with slightly more discomfort despite having a quicker onset of action. Animal studies show Botox to have a better safety margin than Dysport and BT type B. Refer to the chart below for a non-exhaustive list of side effects for both types.
Did you know botulinum toxin Type B can help when Type A fails?
There are number of instances where patients may be unresponsive to the treatment after repeat injections. An antibody test can determine if an individual has developed antibodies against the neurotoxin. Patients who have developed resistance to BT type A may experience efficacious results from BT type B injections but may soon develop resistance to it as well. Neutralizing antibodies can inhibit the biological activity of botulinum toxin. Immunogenicity of BT products are assessed by the following tests:
- EDB (extensor digitorum brevis) assay;
- FTAT (frontalis antibody test);
- UBI (unilateral brow injection);
- ELISA assay;
- MNA (mouse neutralization assay).
Do They Cost The Same?
The average cost for BT type B injection at 5000 units/mL is around $312. The cost for BT type A injections ranges from $300 to $1,200 in the US.
Botulinum toxin therapy is a simple and effective modality for upper and lower face wrinkles. It is a cost-effective alternative to surgical procedures. With new studies emerging regularly, the market is hoping to develop products with longer duration and increased efficacy. Research and development of these products is an exciting and promising frontier in the cosmetic industry.