INTRODUCTION
As with other organs of the body, the skin undergoes
changes with aging. Unlike other organs, however,
the skin is visible and, usually, an easy indicator of a
person’s age. In fact, several studies have concluded that facial
attributes such as skin uniformity are among the most important
factors in estimating a person’s age.1-3 Signs of facial aging,
such as rhytides and folds, can be caused by photoaging, smoking,
facial expressions, and environmental factors. To address
the aging face, numerous cosmetic procedures are available.
Of these cosmetic procedures, treatment with botulinum toxin
Type A (BoNTA) for the correction of hyperdynamic wrinkles
is the most common, with more than 3 million procedures
performed each year.4 BoNTA, as well as other cosmetic procedures,
are commonly used in patients of various ethnicities;
in 2012, non-Caucasians constituted 21% of all cosmetic procedures.
4 Despite the use of BoNTA among patients with skin
of color, the number of these patients enrolled in clinical trials
does not reflect the percentage of patients with skin of color
in the population who receive cosmetic correction with toxin.
Several studies have investigated the use of the first two BoNTA
products – onabotulinumtoxin A [Botox® (BTX); Allergan,
Irvine, CA] and abobotulinumtoxin A [Dysport® (DYS); Medicis
Aesthetics, Scottsdale, AZ] – in non-Caucasian populations.5, 6
However, the latest BoNTA product, incobotulinumtoxin A [Xeomin
® (XEO); Merz North America, Greensboro, NC] has not
been widely reported in these populations to date.
It is important to understand the safety and efficacy of BoNTA
products in non-Caucasian patients, as the skin of those individuals
with Fitzpatrick skin types IV to VI may age differently
than the skin of individuals with fairer skin. Studies that have
investigated skin types IV to VI suggest that the protective
pigmentation of types IV to VI may cause the effects of photodamage
to occur 10 to 20 years later, often with less severity,
than those with types I to III.7-11 Premature aging can occur in
types IV to VI but typically will manifest as midfacial aging instead
of the photodamage that is characteristic of lighter skin.12
Because of this difference in response, persons with darker
skin types potentially may be more responsive to BoNTA than
Caucasians (by achieving greater change from baseline on glabellar
severity ratings). In studies of BTX and DYS specifically,
African Americans, who constituted nearly 20% of the study
population, had a higher response rate to DYS than the general
population.13 These results were consistent with those of Brandt
and colleagues. The 51% of non-Caucasian subjects in the trial
demonstrated a higher proportion of response to DYS than the
Caucasian subjects demonstrated.5
XEO was studied in Caucasians and non-Caucasians in 2 pivotal
trials in 16 clinical sites in the United States and Canada.
These studies, which supported the approval of XEO in the
United States in 2011, are commonly referred to as GL-1 and
GL-2; a total of 547 patients were enrolled in these studies and
were primarily Caucasian (89% and 65%, respectively).14 In
