Forms of Botulinum Neurotoxin

Two forms of botulinum neurotoxin are available for patients. These are botulinum neurotoxin type A (trade names Botox, Dysport, and Xeomin) and botulinum neurotoxin type B (trade names Myobloc and Neurobloc).

Other 'serotypes' of botulinum neurotoxin are under investigation as potential therapeutic agents. These include (in addition to types A and B) types C, D, E, F, and G. Each one has different properties and actions. No two are exactly alike. At present, type F is the only additional form that has shown some promise as a viable treatment for humans.

Although the overall effect is similar, the specific mechanism by which each serotype achieves this effect is different. For example, both type A and type B block the neurotransmitter acetylcholine, but they do so by breaking up different proteins within the nerve cell.

Botulinum neurotoxin type A is commercially available in the United States as Botox from Allergan, Inc, Dysport from Ipsen, Ltd, and Xeomin from Merz. Botulinum type B is available from Solstice Neurosciences/US WorldMeds as Myobloc in the United States, and as Neurobloc abroad.

Botulinum neurotoxin type A is approved by the US Food and Drug Administration (FDA) or the treatment of blepharospasm and cervical dystonia. Botulinum neurotoxin type-B is approved in the US for the treatment of cervical dystonia. Both type A and type B are used extensively to treat the various forms of dystonia. The regulations of the FDA allow physicians to use approved medications for conditions other than the specified indications. This is called "off-label" use.

No studies have been done to examine the effects of botulinum neurotoxin during pregnancy. It is generally recommended that women not receive botulinum neurotoxin injections while pregnant.

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