What is botulinum toxin?

The bacterial botulinum toxin refined into a drug called Botox, among other formulations. It can smooth fine lines and wrinkles by paralyzing underlying facial muscles, it can reduce nerve pain and relax spasming muscles.
The bacterial botulinum toxin refined into a drug called Botox, among other formulations. It can smooth fine lines and wrinkles by paralyzing underlying facial muscles, it can reduce nerve pain and relax spasming muscles.

Botulinum toxin is one of nature’s most poisonous biological substances. It is a neurotoxin produced by bacteria known as Clostridium botulinum. The neurotoxin binds to the nerve terminals attached to the muscles, disrupts nerve signals, and causes muscle weakness and paralysis.

Botulinum toxin, known as the miracle poison, has therapeutic benefits when used in minute quantities. The toxin works as a muscle relaxant and as a treatment for certain neuromuscular diseases, as well as for smoothing out wrinkles caused by aging.

Crude botulinum toxin is purified and diluted with human serum albumin before use on people. There are seven identified types of botulinum toxin, named A to G, with two sub-types in C. Currently, types A and B are used in the preparation of botulinum toxin injections.

Researchers have discovered an eighth type named ‘H’, the deadliest substance of the group so far. It does not have an antidote, and for the first time ever, with government approval, the scientists have elected to keep the DNA sequence for creating it secret from public databases.

Where is botulinum toxin found?

The spores produced by Clostridium botulinum bacteria are commonly found all around us in the soil, plants, water and animal intestinal tracts, and harmless for the most part. When the bacterial spores find the right environment, they germinate, grow and excrete the deadly botulinum toxin.

What is botulism?

Even a small amount of botulinum toxin is highly toxic and can lead to botulism. Botulism is a rare, but serious and potentially fatal condition causing paralysis of the muscles, including the respiratory muscles. Human botulism is caused by types A, B, E, and rarely, F.

Botulism may be of four kinds:

  • Foodborne botulism from improperly processed canned food, contaminated by C. botulinum.
  • Wound botulism: Infection of an open wound by C. botulinum.
  • Infant botulism occurs when C. botulinum spores are ingested by infants under six months, whose gut flora has yet to develop.
    • The term “gut flora” refers to the beneficial community of bacteria that live in a healthy person’s intestinal tract. 
    • This community supports immune function and digestion, but must develop through bacterial exposure during childhood.
  • Inhalation botulism caused by accidental or intentional inhalation (such as bioterrorism) of C. botulinum.

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How does botulinum toxin work?

Muscles contract when signaled by nerve terminals with the release of a chemical known as acetylcholine. Acetylcholine is the principal neurotransmitter at neuromuscular junctions. Botulinum toxin blocks the release of acetylcholine to prevent muscle contraction. 

Drugs prepared from botulinum toxin are injected in microscopic amounts in specific muscles that require treatment. The drug binds to the nerve terminals and blocks the release of acetylcholine, relaxing the targeted muscles.

The blockage of acetylcholine is irreversible as the toxin destroys the function of the cholinergic nerve terminals. The muscle can recover function in about two to three months, however, when new nerve terminals develop and start releasing acetylcholine (re-innervation). Therapeutic/cosmetic injections are usually repeated every three or four months. The muscle atrophies to some extent with each injection.

Ongoing studies show that botulinum toxin also blocks release of certain other neurotransmitters such as glutamate and substance P, and reduces the sensation of pain. Botulinum toxin’s pain relieving properties are not completely understood, however.

What is botulism toxin used for?

Botulinum toxin has cosmetic and therapeutic uses. Researchers continue to conduct clinical trials for its use in an ever-widening range of conditions, including pain management in certain chronic pain disorders.

The potential therapeutic uses of botulinum toxin injection include:

Focal dystonia

Focal dystonia is involuntary, persistent and uncontrollable muscle contraction, which causes abnormal postures. Types of focal dystonia treated with botulinum toxin injections include:

  • Cervical dystonia: Also known as spasmodic torticollis, a painful condition in which neck muscles contract and twist the head to one side)
  • Blepharospasm: Involuntary eye twitching or blinking
  • Laryngeal dystonia: Uncontrolled spasms of the laryngeal muscles
  • Limb dystonia: Involuntary contraction of arms and limbs
  • Oromandibular dystonia: Contraction of jaw and other facial muscles
  • Orolingual dystonia: Contraction of muscles in the lower face, mouth and tongue
  • Truncal dystonia: Contraction of spinal, abdominal and chest muscles

Spasticity

Spasticity is a condition in which muscles become tight and stiff, preventing normal movement. Studies have shown that botulinum toxin injections are effective in treatment of spasticity caused by conditions that include:

Nondystonic disorders

Following are some of the nondystonic disorders in which muscle contractions may be treated with botulinum toxin injections:

  • Hemifacial spasm (muscle twitching on one side of the face)
  • Tremor
  • Tics
  • Myokymia (involuntary quivering of localized muscles)
  • Synkinesis (a voluntary muscle movement causing involuntary movement of another muscle)
  • Tinnitus (ringing in the ears caused by twitching of inner ear muscles)
  • Hereditary muscle cramps
  • Nocturnal bruxism (teeth grinding in sleep)
  • Trismus (lockjaw)
  • Anismus (tightening of pelvic floor muscles making bowel movement difficult)
  • Strabismus (crossed eye)
  • Nystagmus (involuntary, repetitive eye movement which can cause vision problems)

Chronic pain

Botulinum toxin use for pain management in many conditions is still in clinical trials. Only migraine headache has FDA approval for botulinum toxin use to relieve pain. Following are some of the conditions in which chronic pain and localized muscle spasms may be treated with botulinum toxin injection:

Smooth muscle hyperactive disorders

Smooth muscles are found in internal organs and blood vessels and help in their function. Conditions involving smooth muscles that may be treated with botulinum toxin injections include:

Cosmetic use

Botulinum toxin injections are commonly used for cosmetic purposes such as:

  • Glabellar lines (frown lines) and canthal lines (crow's feet) from aging
  • Neck bands from aging (platysma muscle bands)

Other disorders

Other disorders involving sweating, salivation and allergies that can be treated with botulinum toxin injections are:

QUESTION

Medically speaking, the term "myalgia" refers to what type of pain? See Answer

What are the FDA-approved botulinum toxin drugs?

OnabotulinumtoxinA (Botox, Botox Cosmetic)

Botox is approved for

Botox Cosmetic is approved for

  • Moderate to severe glabellar lines
  • Moderate to severe lateral canthal lines

AbobotulinumA (Dysport)

Approved for

  • Upper and lower limb spasticity
  • Cervical dystonia
  • Moderate to severe glabellar lines
  • Lower limb spasticity in children aged 2 years or older

IncobotulinumtoxinA (Xeomin)

Approved for

  • Upper and lower limb spasticity
  • Cervical dystonia
  • Blepharospasm
  • Moderate to severe glabellar lines
  • Chronic sialorrhea

PrabotulinumtoxinA (Jeuveau)

  • Approved for moderate to severe glabellar lines.

RimabotulinumtoxinB (Myobloc)

  • Approved for cervical dystonia

What are the side effects of botulinum toxin drugs?

Botulinum toxin injection is well-tolerated and side effects are mostly mild and temporary. Side effects of botulinum toxin drugs include:

Botulinum toxin when used for cervical dystonia may cause complications such as:

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Summary

Botulinum toxin is one of nature’s most poisonous biological substances. It is a neurotoxin produced by bacteria known as Clostridium botulinum. The neurotoxin binds to nerve terminals controlling muscles, disrupts nerve signals, and causes muscle weakness and paralysis. These effects can be harnessed therapeutically to relax spasming muscles, reduce wrinkles, and deaden neuropathic pain.

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Medically Reviewed on 7/20/2020
References
Medscape Medical Reference

The New Scientist
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