Botox Cosmetics Newcastle
Botulinum toxin (BTX) is a neurotoxic protein produced by the bacterium Clostridium botulinum and related species. It prevents the release of the neurotransmitter acetylcholine from axon endings at the neuromuscular junction and thus causes flaccid paralysis. Infection with the bacterium causes the disease botulism. The toxin is also used commercially in medicine, cosmetics and research.
Botulinum is the most acutely lethal toxin known, with an estimated human median lethal dose (LD50) of 1.3–2.1 ng/kg intravenously or intramuscularly and 10–13 ng/kg when inhaled.
There are eight types of botulinum toxin, named type A–H. Type A and B are capable of causing disease in humans, and are also used commercially and medically. Types C–G are less common; types E and F can cause disease in humans, while the other types cause disease in other animals. Type H is considered the deadliest substance in the world – an injection of only 2-billionths of a gram (2 ng) can cause death to an adult. Botulinum toxin types A and B are used in medicine to treat various muscle spasms and diseases characterized by overactive muscle. The commercial form is marketed under the brand name Botox, among others.
|IM (approved), SC, intradermal, into glands|
|Chemical and physical data|
|Molar mass||149 kg/mol (149,321g/mol)|
Botulinum toxin is used to treat a number of problems.
Botulinum toxin is used to treat a number of disorders characterized by overactive muscle movement, including post-stroke spasticity, post-spinal cord injury spasticity, spasms of the head and neck, eyelid, vagina, limbs, jaw, and vocal cords. Similarly, botulinum toxin is used to relax clenching of muscles, including those of the oesophagus, jaw, lower urinary tract and bladder, or clenching of the anus which can exacerbate anal fissure. It may also be used for improper eye alignment. Botulinum toxin appears to be effective for refractory overactive bladder.
Other muscle disorders
Strabismus is caused by imbalances in the actions of muscles that rotate the eyes, and can sometimes be relieved by weakening a muscle that pulls too strongly, or pulls against one that has been weakened by disease or trauma. Muscles weakened by toxin injection recover from paralysis after several months, so it might seem that injection would then need to be repeated. However, muscles adapt to the lengths at which they are chronically held, so that if a paralyzed muscle is stretched by its antagonist, it grows longer, while the antagonist shortens, yielding a permanent effect. If there is good binocular vision, the brain mechanism of motor fusion, which aligns the eyes on a target visible to both, can stabilize the corrected alignment.
In January 2014, botulinum toxin was approved by UK’s Medicines and Healthcare Products Regulatory Agency (MHRA) for treatment of restricted ankle motion due to lower limb spasticity associated with stroke in adults.
On July 29, 2016, Food and Drug Administration (FDA), of the United States of America approved abobotulinumtoxinA for injection for the treatment of lower limb spasticity in pediatric patients two years of age and older. AbobotulinumtoxinA is the first and only FDA-approved botulinum toxin for the treatment of pediatric lower limb spasticity. In the United States of America, the FDA approves the text of the labels of prescription medicines. The FDA approves which medical conditions the drug manufacturer may sell the drug for. However, those approved by the FDA to prescribe these drugs may freely prescribe them for any condition they wish, called off-label use. Botulinum toxins have been used off-label for several pediatric conditions, including infantile esotropia.
In 2010, the FDA approved intramuscular botulinum toxin injections for prophylactic treatment of chronic migraine headache.
In cosmetic applications, botulinum toxin is considered safe and effective for reduction of facial wrinkles, especially in the uppermost third of the face. Injection of botulinum toxin into the muscles under facial wrinkles causes relaxation of those muscles, resulting in the smoothing of the overlying skin. Smoothing of wrinkles is usually visible three days after treatment and is maximally visible two weeks following injection. The treated muscles gradually regain function, and generally return to their former appearance three to four months after treatment. Muscles can be treated repeatedly to maintain the smoothed appearance.
Botulinum toxin is also used to treat disorders of hyperactive nerves including excessive sweating, neuropathic pain, and some allergy symptoms. In addition to these uses, botulinum toxin is being evaluated for use in treating chronic pain.
While botulinum toxin is generally considered safe in a clinical setting, there can be serious side effects from its use. Most commonly, botulinum toxin can be injected into the wrong muscle group or spread from the injection site, causing paralysis of unintended muscles.
Side effects from cosmetic use generally result from unintended paralysis of facial muscles. These include partial facial paralysis, muscle weakness, and trouble swallowing. Side effects are not limited to direct paralysis however, and can also include headaches, flu-like syndromes, and allergic reactions. Just as cosmetic treatments only last a number of months, paralysis side-effects can have the same durations. At least in some cases, these effects are reported to dissipate in the weeks after treatment. Bruising at the site of injection is not a side effect of the toxin but rather of the mode of administration, and is reported as preventable if the clinician applies pressure to the injection site; when it occurs, it is reported in specific cases to last 7–11 days. When injecting the masseter muscle of the jaw, loss of muscle function can result in a loss or reduction of power to chew solid foods.
Side effects from therapeutic use can be much more varied depending on the location of injection and the dose of toxin injected. In general, side effects from therapeutic use can be more serious than those that arise during cosmetic use. These can arise from paralysis of critical muscle groups and can include arrhythmia, heart attack, and in some cases seizures, respiratory arrest, and death. Additionally, side effects which are common in cosmetic use are also common in therapeutic use, including trouble swallowing, muscle weakness, allergic reactions, and flu-like syndromes.
In response to the occurrence of these side effects, in 2008 the U.S. FDA notified the public of the potential dangers of botulinum toxin as a therapeutic. Namely, they warned that the toxin can spread to areas distant from the site of injection and paralyze unintended muscle groups, especially when used for treating muscle spasticity in children treated for cerebral palsy. In 2009, the FDA announced that boxed warnings would be added to available botulinum toxin products, warning of their ability to spread from the injection site. Additionally, the FDA announced name changes to several botulinum toxin products, meant to emphasize that the products are not interchangeable and require different doses for proper use. Botox and Botox Cosmetic were renamed onabotulinumtoxinA, Myobloc was renamed rimabotulinumtoxinB, and Dysport name renamed abobotulinumtoxinA. In conjunction with this, the FDA issued a communication to health care professionals reiterating the new drug names and the approved uses for each A similar warning was issued by Health Canada in 2009, warning that botulinum toxin products can spread to other parts of the body.
Role in disease
Botulinum toxin produced by Clostridium botulinum is the cause of botulism. Humans most commonly ingest the toxin from eating improperly-canned foods in which C. botulinumhas grown. However, the toxin can also be introduced through an infected wound. In infants, the bacteria can sometimes grow in the intestines and produce botulinum toxin within the intestine and can cause a condition known as floppy baby syndrome. In all cases, the toxin can then spread, blocking nerves and muscle function. In severe cases, the toxin can block nerves controlling the respiratory system or heart, resulting in death. Botulism can be difficult to diagnose, as it may appear similar to diseases such as Guillain–Barré syndrome, myasthenia gravis, and stroke. Other tests, such as brain scan and spinal fluid examination, may help to rule out other causes. If the symptoms of botulism are diagnosed early, various treatments can be administered. In an effort to remove contaminated food which remains in the gut, enemas or induced vomiting may be used. For wound infections, infected material may be removed surgically. Botulinum antitoxin is available and may be used to prevent the worsening of symptoms, though it will not reverse existing nerve damage. In severe cases, mechanical respiration may be used to support patients suffering from respiratory failure. The nerve damage heals over time, generally over weeks to months. With proper treatment, the case fatality rate for botulinum poisoning can be greatly reduced.
Two preparations of botulinum antitoxins are available for treatment of botulism. Trivalent (A,B,E) botulinum antitoxin is derived from equine sources using whole antibodies. The second antitoxin is Heptavalent (A,B,C,D,E,F,G) botulinum antitoxin, which is derived from equine antibodies which have been altered to make them less immunogenic. This antitoxin is effective against all known strains of botulism.
Mechanism of action
Botulinum toxin exerts its effect by cleaving key proteins required for nerve activation. First, the toxin binds specifically to nerves which use the neurotransmitter acetylcholine. Once bound to the nerve terminal, the neuron takes up the toxin into a vesicle. As the vesicle moves farther into the cell, it acidifies, activating a portion of the toxin which triggers it to push across the vesicle membrane and into the cell cytoplasm.Once inside the cytoplasm, the toxin cleaves SNARE proteins preventing the cell from releasing vesicles of neurotransmitter. This stops nerve signaling, leading to paralysis.
The toxin itself is released from the bacterium as a single chain, then becomes activated when cleaved by its own proteases. The active form consists of a two-chain protein composed of a 100-kDa heavy chain polypeptide joined via disulfide bond to a 50-kDa light chain polypeptide. The heavy chain contains domains with several functions: it has the domain responsible for binding specifically to presynaptic nerve terminals, as well as the domain responsible for mediating translocation of the light chain into the cell cytoplasm as the vacuole acidifies. The light chain is a zinc metalloprotease and is the active part of the toxin. It is translocated into the host cell cytoplasm where it cleaves the host protein SNAP-25, a member of the SNARE protein family which is responsible for fusion. The cleaved SNAP-25 is unable to mediate fusion of vesicles with the host cell membrane, thus preventing the release of the neurotransmitter acetylcholine from axon endings. This blockage is slowly reversed as the toxin loses activity and the SNARE proteins are slowly regenerated by the affected cell.
The seven toxin types (A-G) have different tertiary structures and sequence differences. While the different toxin types all target members of the SNARE family, different toxin types target different SNARE family members. The A, B, and E serotypes cause human botulism, with the activities of types A and B enduring longest in vivo (from several weeks to months).
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