By Miki Omori BSN, RN
Neurotoxins such as Botox, Xeomin, and Dysport are injected into facial muscles to cause a temporary relaxation of the muscles. Neurotoxins are primarily used to reduce and diminish wrinkles and creases but can also be used preventatively to prevent the development of fine lines, wrinkles and facial slimming. Neurotoxins can also be used to treat excessive sweating.
These neurotoxins are derived from one of the worlds poisonous biological substances produced by a bacterium Clostridium botulinum. This neurotoxin was first used to correct strabismus (crossed eyes) in humans and was then approved for its use in the treatment of spastic disorders. Botox, Botulinum toxin-A, was then approved in 2002 for cosmetic use for the use or temporary reduction of frown lines.
Mechanism of Action
Muscle movement or contraction is the product of a cell signaling pathway that results in the release of Acetylcholine by nerve endings at the neuromuscular junction. This release of Acetylcholine then triggers a cascade of effects that causes muscle contraction. When a neurotoxin is administered intramuscularly, the botulinum toxin binds and acts on the neuromuscular junction and inhibits the release of acetylcholine causing muscle paralysis. The paralytic effect of neurotoxins occurs around four to seven days after injections. The blockage of the nerve endings is irreversible, but function of muscle contraction returns due to formation of new nerve terminals which takes two to three months.
Preparation and Storage
Botox is the first neurotoxin to become commercially available in the United States and its safety is well established. It is stored in a freezer at or below -5oC. It is then reconstituted using sterile saline. Once reconstituted, it is then kept in a refrigerator until it is used. Similar to Botox, Dysport is stored in the freezer. Once reconstituted, it can be stored in the refrigerator but must be used within 24 hours. Xeomin is stored at room temperature until reconstituted and is then refrigerated.
The botulinum toxin itself has a molecular weight of 150 kDa. It is then further purified resulting in Botox, Dysport and Xeomin. Botox is the largest of the three neurotoxins at approximately 900 kDa. The accessory or protective proteins are further purified resulting in Dysport which is roughly 800 kDa and Xeomin is 150 kDa. The lack of accessory proteins in Xeomin is said to help prevent resistance overtime, however, due to its small size, it has the potential to diffuse a greater distance and as a result makes the injection the least precise. On the other hand, theoretically, Botox is the most precise of the three neurotoxins due to its protective proteins. The injector will carefully administer the neurotoxin based on the molecular makeup of neurotoxin used. The onset of action also differs. Dysport is the fastest to take action at around 24 hours, Botox at around 72 hours and Xeomin at around 4 days.
Treatment with neurotoxins are generally well tolerated. There can be mild pain and bruising at injection sites, headache, or mild nausea but should subside within a few hours. Weakness or mild paralysis in neighboring musculature is possible but usually resolve in a couple of months. It is reported that 1-3% of patients have experienced temporary upper lid and brow ptosis which results from the diffusion or migration of neurotoxins. It is recommended to remain upright for four hours following treatment to decrease diffusion. It is also recommended to avoid working out for 6 hours after treatment and avoid facial treatments for at least 10 days.