wrinkles. It is also effective in reducing pain from headaches,
back pain related to muscle spasms, neck pain, etc. The
mechanism of the drug's action is that it is taken up into the
end of the motor nerve and blocks the release of
acetylcholine. Acetylcholine is the chemical that acts on the
muscle to initiate a muscle contraction. Whereas that
particular nerve ending will not function again after Botox, the
nerve attempts to regenerate by "sprouting", that is the
development of new nerve shoots which reattach to the
muscle. However sprouting takes 3-6 months to occur,
therefore the activity of Botox is 3-6 months.
In addition to reducing muscle spasm and contraction,
Botox also blocks pain directly through several other
systems, although the degree of this action is not clearly
defined.
There are 7 isomers of botulinum which is food poisoning.
Botox is the "A" isomer, and is extremely potent. Only a few
billionths of a gram are required to stop muscle contraction.
There are other isomers also such as the "B" isomer known
commercially as Myoblock. It is not as potent as Botox, but
is available as a premixed liquid.
For large muscle groups or for muscles in the front of the
neck, it is very useful to have electromyelogram guidance of
the needle placement into the location where the nerve comes
into the muscle. Typically we use a neurologist to provide
such injections since they are familiar with EMG techniques.
Side effects are usually minor and consist of mild malaise,
muscle soreness for a week in some patients, and with very
large doses, nausea.
The onset of the effect is 3-7 days after the injection and
the injection lasts up to 6 months, then may be repeated.
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