Botulinum toxin: historical perspective and potential new indications.

Botulinum toxin (BTX), a purified form of the neurotoxin responsible for botulism, is used worldwide for the treatment of abnormal muscle contractions. The ability of BTX to block acetylcholine release in a long-lasting but reversible fashion with few side effects has made it an important tool in a wide variety of neuromuscular disorders, including the dystonias, tremor, tics, and spasticity. There are seven antigenically distinct toxins. BTX-A has been in clinical use for almost two decades, with an outstanding efficacy and safety profile. Clinical effects are often seen within 1 week of injection, and benefits typically last from 3-6 months. Patient selection and the proper choice of dose and administration site are the most important determinants of a favorable response to BTX treatment.