What is a Botox Injection anyway?
The cosmetic form of botulinum toxin, often referred to by its
product name Botox, is a popular non-surgical injection that
temporarily reduces or eliminates frown lines, forehead creases,
crows feet near the eyes and thick bands in the neck. The toxin
blocks the nerve impulses, temporarily paralyzing the muscles
that cause wrinkles while giving the skin a smoother, more
refreshed appearance. Studies have also suggested that Botox is
effective in relieving migraine headaches, excessive sweating
and muscle spasms in the neck and eyes. Botulinum neurotoxin is
produced by the gram-negative anaerobic bacterium Clostridium
botulinum. Eight serologically distinct botulinum neurotoxins
exist, designated as A, B, C1, C2, D, E, F, and G. Seven are
associated with paralysis. Types A, B, E and, rarely, F and G
are associated with human botulism. Dose The dose of botulinum
toxin is expressed in mouse units. One unit is equal to the
amount that will kill 50% of a group of 18- to 22-g Swiss
Webster mice when injected intraperitoneally. The human lethal
dose (LD) for BOTOX (botulinum type A purified neurotoxin
complex) is estimated at approximately 3000 units. BOTOX
injections of less than 100 units usually are used for cosmetic
purposes and of less than 300-600 units for other purposes,
thereby allowing a wide safety margin. Recognizing that doses
are not interchangeable among different formulations of
botulinum toxin (BOTOX, Dysport, Myobloc) is important; to
achieve similar clinical effects, different doses are used.
Botulinum toxin formulations BOTOX is a sterile lyophilized form
of botulinum toxin type A. It is produced from a culture of the
Hall strain of C botulinum and purified by a series of acid
precipitations to a crystalline complex containing the toxin and
other proteins. The FDA approved BOTOX in December 1989 as an
orphan drug for the treatment of strabismus, hemifacial spasms,
and blepharospasm. BOTOX is distributed in 100-unit vials. The
original batch of neurotoxin prepared by Shantz in November 1979
(designated batch 79-11) constituted the original BOTOX
formulation and was used until December 1997. It was replaced by
a new neurotoxin complex batch designated BCB 2024. The new bulk
batch is 5-6 times more potent on a weight basis. In a 100-unit
vial, only 4.8 ng of neurotoxin is needed compared to 25 ng of
79-11. The new BOTOX is comparable in clinical efficacy and
safety to the old, and a unit dose of new BOTOX provides an
equivalent response to the same unit dose of old BOTOX.
Hopefully, the reduced protein load of the new BOTOX leads to
reduced immunogenicity and a lower incidence of neutralizing
antibody formation. Dysport is another formulation of botulinum
toxin type A available in Europe and a few other countries. It
is prepared using column-based purification techniques and
distributed in 500-unit vials that can be stored at room
temperature. BOTOX and Dysport are both botulinum toxin type A
preparations but are quite distinct from one another. BOTOX is
approximately 4 times more potent on a per unit basis, and
Dysport doses often are approximately 4 times the BOTOX doses
used to generate a similar clinical effect. Differences in these
toxins may relate to differences in the strain of bacterium,
preparation, diffusion, and potency testing. Myobloc is a
botulinum toxin type B preparation currently in clinical trials.
It is anticipated that it will be distributed as a solution.
Little information is available concerning the cosmetic use of
Dysport and Myobloc. The remainder of this article therefore
focuses on BOTOX, and all unit doses refer to BOTOX unless
otherwise specified. Reconstitution and storage Store BOTOX in a
freezer at or below -5