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    Research allows better understanding of botulinum toxins' efficacy, onset of action

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    Dr. Gold
    The basic parameters that are said to differentiate neurotoxins from one another include onset of action, time to maximum take and longevity of effect, all of which can vary depending on the individual dose and dilution of a given product. And newer products such as Xeomin (incobotulinumtoxinA, Merz) and PurTox (yet to be approved by the Food and Drug Administration; Mentor) try to differentiate themselves further by claiming to contain pure toxin, free of complexing proteins that may be safer, says Michael H. Gold, M.D., a cosmetic and dermatologic surgeon and medical director of Gold Skin Care Center, Tennessee Clinical Research Center and The Laser and Rejuvenation Center, Nashville, Tenn.

    "These toxins do not have the hemagglutinin part of the molecule, which means theoretically, they should have less antigenicity. Although we have never had significant problems with Botox (onabotulinumtoxinA, Allergan) and Dysport (abobotulinumtoxinA, Medicis) in this regard, these newcomers may be potentially safer than what we have now, which again, is very safe," Dr. Gold says.

    XEOMIN, BOTOX STUDY A relatively recent head-to-head study funded by Merz investigated the noninferiority of Xeomin to Botox in the treatment of glabellar frown lines (Sattler G, Callander MJ, Grablowitz D, et al. Dermatol Surg. 2010;36(Suppl 4):2146-2154). The prospective, multicenter, international, rater- and patient-blind trial included 381 patients who were randomized into two groups in a 3:1 (incobotulinumtoxinA:onabotulinumtoxinA) ratio to receive a total of 24 units of Xeomin or 24 units of Botox (a clinical dose-conversion ratio of 1:1).

    Efficacy endpoints included the percentage of responders at maximum frown at weeks four and 12 as assessed by the investigators, as well as a panel of independent raters based on standardized digital photographs.

    Results showed that both of the neurotoxin preparations were equally effective in the treatment of glabellar frown lines. At four weeks after injection, response rates at maximum frown were 96.4 percent in the incobotulinumtoxinA group and 95.7 percent in the onabotulinumtoxinA group as assessed by independent raters.

    NON-BRANDED WARNING In order to provide the safest treatments possible, Dr. Gold recommends that physicians refrain from using non-branded toxins without FDA approval or CE mark.

    "Today, there are hundreds of non-branded neurotoxins available on the market; however, I would strongly advise against using them because it is much safer to use toxins that have gone under FDA scrutiny. Physicians need to uphold the standard of care, and these non-branded toxins may not fit that bill," Dr. Gold says.


    Dr. Nestor
    TRANSDERMAL ADVANCEMENTS Along with the development of new neurotoxins, companies are also researching new ways to deliver these products beyond the needle. According to Dr. Gold, a topical toxin could have great therapeutic value for a variety of patients, particularly those with hyperhidrosis, where repeated neurotoxin injections can be painful.

    Revance Therapeutics is developing a topical botulinum toxin type A product using its patented TransMTS transdermal peptide technology, which is under investigation for the treatment of crow's feet wrinkles and axillary hyperhidrosis.

    Ionic Nano Particle Technology (INParT), developed by Transdermal Corp., is another transdermal delivery system that can aid in the delivery of a variety of active compounds to target sites in the skin and beyond. Though early in development, this delivery system is showing positive results when used with a variety of active products, including topical anesthetics, hyaluronic acids and neurotoxins, says Mark Nestor M.D., Ph.D., voluntary associate professor, department of dermatology and cutaneous surgery, University of Miami Miller School of Medicine.

    "Nanotechnology is not limited to only one product, and for the past three years, we have done work with cross-linked and non-cross-linked hyaluronic acids and with numerous botulinum toxins currently available on the market, including Myobloc (rimabotulinumtoxinB, Solstice Neurosciences), Botox, Dysport and Xeomin," Dr. Nestor says.

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