The four botox products are as follows:
1) Botox by Allergan
2) Myobloc by Solstice Neurosciences
3) Dysport by Ipsen, Ltd
4) Xeomin by Merz
Obviously, Botox by Allergan was the first and most popular to the point where its product name "botox" is being used interchangeably to mean any botulinum toxin product; much like "Kleenex" is used to mean any tissue product to blow the nose with or "Google" to mean "to search for" even if you use Bing.
Although all four products are made from the Clostridium botulinum bacteria, the four products are isolated from different strains of bacteria, have different molecular structures, and attach to different parts of the nerve. What does this mean for the end-user? It means that dosages are not equivalent across product lines. In other words, 1 unit of botox is NOT the same as 1 unit of myobloc. Furthermore, duration of effect may be different as well as immune response.
Also as an FYI, Botox, Xeomin, and Dysport are Botulinum toxin type A whereas Myobloc is type B.
Dr. Chang performs botox injections for a variety of problems using Botox by Allergan.
At least for spasmodic dysphonia, the conversion factor is 52.3:1 Myobloc (BTX-B) to Botox (BTX-A)