Botulinum toxin, the culprit behind outbreaks of deadly botulism throughout history is also a very useful pharmaceutical agent.
The toxin causes paralysis which is clearly dangerous if it affects large muscle groups, but injecting a small dose in a targeted area can create a desired therapeutic effect.
Botox is known to many people as a cosmetic agent, to relax facial muscles that cause wrinkles, but it has a variety of other medical uses as well. Cosmetic use of the drug, also known as onabotulinumtoxinA, actually led to the discovery that patients with migraine headaches could also benefit. Patients who received facial injections of onabotulinumtoxinA reported significant improvement in migraine or chronic headache pain. The toxin induces a chemical denervation, blocking the release of pain-inducing neuropeptides like substance P and CGRP.
This toxin is also effective at controlling overactive bladder in patients who experience involuntary contractions of the muscles that control the bladder.
It can be used to treat spasticity, a condition characterized by tight, stiff muscles in the limbs or neck and an inability to control the muscles. This occurs with conditions such as cerebral palsy, stroke, multiple sclerosis, or brain injury.
Blepharospasm, a condition affecting eye muscles that leads to excessive and involuntary eye closure, can be controlled with injections of botulinum toxin. This allows patients to avoid functional blindness and complications like corneal abrasions.
It may be useful for other conditions such as carpal tunnel syndrome, excessive sweating, and bruxism (teeth grinding) also.
There are currently 4 different formulations of botulinum toxin approved for therapeutic use in the United States. They are onabotulinumtoxinA (Botox®), abobotulinumtoxinA (Dysport®), incobotulinumtoxinA (Xeomin®), and rimabotulinumtoxinB (Myobloc®).
Botulinum toxin is a potent chemical and side effects can be severe and include muscle weakness near where the medicine was injected, trouble swallowing for several months after treatment, muscle stiffness, neck pain, pain in your arms or legs, blurred vision, puffy eyelids, dry eyes, drooping eyebrows, and dry mouth.