Botulinum toxin. From poison to medicine.

Although thousands of people in the world each year continue to be poisoned with botulinum toxin-food-borne, infantile, or wound botulism-the neurotoxin is now sufficiently understood to allow it to be used as a medicinal agent to paralyze specific muscles, giving temporary symptomatic relief from a variety of dystonic neurologic disorders. I review some of the epidemiologic, clinical, and pathophysiologic aspects of botulinum toxin and how the neurotoxin may act as a poison or a medicine.