From the Guidelines
Botox (botulinum toxin) works by blocking the release of acetylcholine, a neurotransmitter that signals muscles to contract, through a mechanism involving the cleavage of proteins essential for acetylcholine release from nerve terminals, as described in the clinical guidelines for diagnosis and treatment of botulism, 2021 1.
Mechanism of Action
The mechanism of action of Botox involves several steps, including:
- Binding to a neuronal cell
- Internalization by means of receptor-mediated endocytosis
- Translocation to the cytosol
- Cleavage of the proteins involved in the release of acetylcholine, specifically SNAP-25, as part of the SNARE complex 1 This process results in the inhibition of acetylcholine release from the presynaptic motor neuron terminal, leading to a characteristic flaccid paralysis.
Clinical Applications
Botox is used to treat various conditions involving muscle overactivity, such as:
- Cervical dystonia
- Blepharospasm
- Spasticity It is also widely used cosmetically to reduce the appearance of wrinkles by relaxing facial muscles.
Effects and Side Effects
The effects of Botox typically last 3-6 months as nerve terminals gradually regenerate and form new connections 1. Side effects are usually localized to the injection site and can include pain, swelling, and temporary weakness in adjacent muscles. Systemic spread is rare but can cause more serious effects like difficulty swallowing or breathing.
Dosage
Dosing varies by indication, with cosmetic applications generally requiring 20-50 units per treatment area, while therapeutic applications may require higher doses.
From the FDA Drug Label
The symptoms are consistent with the mechanism of action of botulinum toxin and may include asthenia, generalized muscle weakness, diplopia, ptosis, dysphagia, dysphonia, dysarthria, urinary incontinence, blurred vision, and breathing difficulties. The mechanism of action of Botox (botulinum toxin) is related to its effect on muscle activity, causing weakness or paralysis of the muscles into which it is injected. This is evident from the symptoms that occur when the toxin spreads beyond the site of local injection, which are consistent with its mechanism of action.
- Key points about the mechanism of action:
- Causes muscle weakness or paralysis
- Affects muscle activity
- Can cause symptoms such as asthenia, generalized muscle weakness, and breathing difficulties when it spreads beyond the injection site 2
From the Research
Mechanism of Action of Botox
- Botox, or botulinum toxin, acts by blocking the presynaptic release of the neurotransmitter acetylcholine at the neuromuscular junction, leading to reversible chemical denervation of the muscle fibre and inducing partial paralysis and atrophy 3.
- The toxin cleaves specific proteins involved in vesicle fusion, preventing the release of acetylcholine, and its therapeutic effect is to weaken muscle 4.
- Botulinum toxin inhibits the release of acetylcholine from nerve terminals by inhibiting transport of the synaptic vesicles, causing functional denervation lasting up to 6 months 5.
- BOTOX® acts by blocking the release of acetylcholine from the synaptic vesicles at the neuromuscular junctions, thereby inhibiting muscle contraction 6.
Effects of Botox
- The effects of Botox are temporary, with the muscle being progressively reinnervated by nerve sproutings 3.
- Botox has been successfully used in various clinical indications, including dystonia, hemifacial spasm, spasticity, and hyperhidrosis 3, 5.
- Botox can cause muscle atrophy, which is reversible and temporary, and repeated chemodenervation with Botox may increase its duration of effect 7.
Therapeutic Uses of Botox
- Botox has been shown to be safe and effective in the treatment of cervical dystonia, dampening or eliminating involuntary muscle activity and improving control of neck movement, pain, and range of motion 4.
- Botox has been used to manage a number of clinical complications like neuromuscular disorders, migraine, and neuropathic pain 6.
- Botox may have a potential role in improving learning and memory, with studies showing that it can boost learning and memory in adult mice in association with enriched circulation of platelets and enhanced density of pyramidal neurons in the hippocampus 6.