The American Academy of Neurology has issued an update to its 2008 guidelines on the use of botulinum toxin for the treatment of spasticity, cervical dystonia, blepharospasm and migraine headache.
Unlike in previous guidelines, the latest update looks beyond the class effects to those of each of the four preparations separately.
The guidelines, published in Neurology and presented at the recent 68th Annual Meeting of the American Academy of Neurology in Vancouver, British Columbia, Canada, recommend for the first time the use of botulinum toxin for the treatment of chronic migraine, evidence for which was insufficient in 2008.
Based on two Class I placebo-controlled trials, onabotulinumtoxinA was found to be effective and well tolerated for reducing the number of headache days in patients with chronic migraine, defined as attacks of 4 hours or more occurring on at least 15 days monthly for at least 3 months. Although the difference was small at between 1.4 and 2.3 fewer headache days with onabotulinumtoxinA, it was significant. Botulinum toxin is also likely to reduce the impact of headache on health-related quality of life after 24 weeks according to one Class I study, with severe Headache Impact Test scores seen in 67.6% of patients given botulinum toxin versus 78.2% of those given placebo.
The evidence was insufficient, however, to compare the effectiveness of onabotulinumtoxinA against topiramate and other formulations of botulinum toxin for chronic migraine. And the guidelines advise against the use of onabotulinumtoxinA for treatment of episodic migraine, based on evidence of its inefficacy, and for tension-type headache due to a lack of evidence.
For blepharospasm, the 2008 guidelines concluded that botulinum toxin as a class was effective. Since then, further evidence from two placebo-controlled studies (Class I and Class II studies) provides support for the superior efficacy of incobotulinumtoxinA and abobotulinumtoxinA, with effects lasting over long periods of up to 16 weeks.
And two studies comparing the different formulations indicate comparable efficacy for incobotulinumtoxinA and onabotulinumtoxinA, leading to recommendations for their use for the treatment of blepharospasm (Level B), while abobotulinumtoxinA is possibly effective and a treatment option (Level C). There is currently insufficient evidence to determine the efficacy of rimabotulinumtoxinB.
RimabotulinumtoxinB is established as effective for cervical dystonia, however, along with abobotulinumtoxinA and both are recommended treatments (Level A). Further evidence since 2008 indicates that incobotulinumtoxinA and onabotulinumtoxinA are probably effective and can also be considered as treatment options (Level B).
Evidence on three of the botulinumtoxinA formulations - abobotulinumtoxinA, incobotulinumtoxinA and onabotulinumtoxinA - demonstrated their efficacy in reducing excess muscle tone in adults with upper limb spasticity and as such should be offered to patients, while rimabotulinumtoxinB is probably effective and a possible treatment option. Currently, the data on the efficacy of the different formulations for improving active function is inadequate and the guidance suggests that this is likely to be highly patient-specific.
The guidelines, authored by David Simpson (Icahn School of Medicine at Mount Sinai, New York, USA) and colleagues, also cite evidence for onabotulinumtoxinA having superior efficacy to tizanidine for the treatment of upper limb spasticity and recommends considering it first.
It also recommends the use of both high-volume, low-potency injections of onabotulinumtoxinA and endplate targeting of the formulation into proximal upper extremity muscles following evidence showing these techniques optimise treatment response.
For lower extremity spasticity in adults, abobotulinumtoxinA and onabotulinumtoxinA should be offered to patients, but evidence to support or refute a benefit with incobotulinumtoxinA or rimabotulinumtoxinB is currently insufficient.
By Lucy Piper
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