Botox has been in use since the late 1970s for the treatment of strabismus and this treatment of spasticity still accounts for more than half of all doses. The doses used for muscle spasticity are considerably greater than for cosmetic uses and hyperhidrosis.
What You Should Know About Possible Adverse Reactions
When it comes to medical use of botulinum toxin injections, systemic reactions away from the injection site and even fatalities have been associated with the injection. However, cause and effect were never established and these patients had significant neuromuscular problems.12
According to the Allergan Web site: “There has not been a confirmed serious case of spread of toxin effect away from the injection site when Botox has been used at the recommended dose to treat chronic migraine, severe underarm sweating, blepharospasm or strabismus, or when Botox Cosmetic has been used at the recommended dose to treat frown lines.”13
Hypersensitivity reactions have been reported but are rare. One fatal case of anaphylaxis may have occurred with Botox or the lidocaine used in the reconstitution.14
The medical benefits of botulinum toxin justify the risk in most cases.12 Over more than 30 years, clinicians collectively have performed millions of botulinum toxin injections. A 2009 FDA review of all botulinum toxin products identified 10 pediatric deaths and 17 adult deaths.15 All of these patients had underlying neuromuscular disorders. Allergan’s Web site notes “the available evidence does not suggest that Botox treatment is associated with an increased risk of mortality.”13
It is uncommon for Botox to result in neutralizing antibodies. One study reports a 0.49 percent incidence and this appears to have very little influence on effectiveness.16 Botulinum toxin products now have a FDA required “black box” warning. While one should take care in the administration of botulinum toxin and keep the dose to the minimum effective dose required, some of the worry might be unjustified.17,18
Relative contraindications to the use of botulinum toxin include: neuromuscular disorders such as amyotrophic lateral sclerosis, myasthenia gravis and Lambert-Eaton syndrome. Known hypersensitivity to ingredients in the product is a rare contraindication.19
Discerning Among The Different Types And Uses Of Botulinum Toxin
Botox, Dysport and Xeomin are all botulinum “A” toxins produced by three different companies. Myobloc is the “B” toxin. Although there is a lack of consensus on this issue, there is little to differentiate between the efficacy of Botox, Dysport and Xeomin. However, the preparations are different and one must keep this in mind when reconstituting the toxins.
While there is some controversy on this, a rough estimate is that between one and three units of Dysport are equivalent to one unit of Botox.20 Again, this is a wide range as there is not yet a consensus on this issue.
Some studies suggest some differences in the duration of action and likelihood of side effects between the BTX-A toxins.21 Some of the difference might be due to uncertainties in volumes of reconstitution and how the formulations have changed over the past few years.21 Myobloc appears to have a more rapid onset but a shorter duration of action than the “A-toxins.”
All the toxins come freeze dried and clinicians must reconstitute these agents. We use the recommended preservative free normal saline. About 10 to 25% of the diluent can be 1% lidocaine and this may decrease the pain of the injections.22