When muscle spasm is chronic, severe and refractory to other treatments it is said to be dystonic. Botulinum toxins such as Botox or Myobloc can be injected to treat painful dystonia. Myobloc (botulinum toxin B) is chemically similar to Botox (botulinum toxin A). Both are used for dystonia. Botox is commonly used for cosmetic applications. Myobloc is used to treat pain caused by chronic muscle dystonica and spasm and can be effective for months at a time. Repeat injections are done no sooner than 3 months because of the risk of you producing antibodies. Injections are performed in the office. No driver is needed. Very small needles are used. Local anesthetic is usually mixed with the Myobloc. Complications are very rare. Common side effects are muscle aches for about a week and dry mouth.