Dystonia

Pharmacologic Treatment of Dystonia

There are a number of treatment options available to treat dystonia. Drugs may be used alone or in combination. In addition, they may be combined with other forms of treatment.

Botulinum toxin (BTX)
Botulinum toxin (BTX) is a biological therapeutic agent that acts against dystonia. Botulinum toxin is a toxic protein that is produced by the bacterium Clostridium botulinum. The use of botulinum toxin (BTX) represents a significant advance in the treatment of dystonia. This toxin is known to cause botulism, a deadly form of food poisoning that is contracted through the ingestion of contaminated food products. However, when a minute amount of commercially prepared BTX is injected directly into an overactive muscle, it relaxes that muscle.

BTX acts to block the release of acetylcholine, a neurotransmitter responsible for activation of muscle contraction. Thus, BTX decreases inappropriate or excessive muscle contractions, allowing the affected area (e.g., arm, neck, leg, eyelid, etc.) to assume a more normal position or posture.

There are seven serotypes of botulinum toxin; namely, types A, B, C, D, E, F, and G. Each serotype has a distinct structure and mechanism of action. In the United States, only two BTX products have been approved by the U.S. Food and Drug Administration (FDA). They are BOTOX® (a BTX-A product produced by Allergan, Inc.) and Myobloc™ (a BTX-B product produced by Solstice Neurosciences). Another BTX-A product–Dysport® (Ipsen, Ltd)–is on the market, but has not been approved by the FDA for use in the United States. Each BTX product is unique, with its own safety, efficacy, and immunogenicity profile.