Update on Botulinum Toxin.
Botulinum toxin type-A (BTX-A) is a neurotoxin which blocks presynaptic release of acetylcholine. It interferes with neuromuscular transmission, temporarily paralyzing the affected muscle. Of special interest for dermatologists is the unlabelled cosmetic applications, for conditions such as wrinkles and hyperhidrosis. Labelled indications in Europe are for cervical dystonia and cerebral palsy. In the US, it is approved for treatment of strabismus, blepharospasm and hemifacial spasm in adults. After repeated use of high doses, antibodies can develop in some individuals, making further treatment ineffective indefinitely. Even when used in high does for neurological conditions, the development of antibodies occurs in < 5&percnt of patients. In 1997, the US FDA approved a new bulk toxin source for use in the manufacture of BTX-A. It has a higher specific potency than original BTX-A formulations, reducing the amount of utilized neurotoxin protein, and thereby reducing antibody production. Another form of this neurotoxin (type B) also appears to be effective in patients who have developed antibodies to BTX-A. It is awaiting US FDA approval for treatment of cervical dystonia.
Carruthers
A
Division of Dermatology, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada.