is observed. Penetrate deeply enough through the dermis and fat layer to reach the target muscle; there should be a slight increase
in resistance to needle penetration at this point. Do not go so deep as to hit the periosteum,18 which may be painful to the patient and may result in headache. If this deep level is reached, withdraw the needle slightly and inject into the muscle.
Degree of Effect
It is possible to dose the glabellar complex to the point that there is an inability for the patient to effect any voluntary movement and an absence of normal facial expressiveness results. It is best to select a dose that will reduce wrinkles yet retain a degree of facial expression. Individual patients may request varying degrees of paresis; for example, an actor may wish to retain a greater degree of facial expression at the expense of some visible wrinkling.
Skin of Color
Genetic differences in the pharmacokinetics of BoNTA and the effects of genetic variation in acetylcholine receptors on BoNTA pharmacodynamics have not been investigated. However, it has been postulated that patients with skin of color could respond differently to BoNTA treatment than white patients owing to genetic variations that manifest as histologic differences in the dermal tissue.17 A pooled analysis comparing patients with skin of color (n=363) with white patients (n=1653) who participated in 3 abobotulinumtoxinA clinical studies found that safety, tolerability,
effectiveness, and patient satisfaction were similar regardless of race.25 A study of onabotulinumtoxinA in 31 black women found that the maximum response rate occurred at
30 days postinjection and diminished through day 120; there was no white patient comparator population in this study.26
Achieving a desired aesthetic outcome with BoNTA therapy requires
a thorough understanding of facial anatomy, individual patient assessment for correct injection placement, and objective assessment of muscle mass for optimal dosing. Men generally have a greater glabellar muscle mass than women and may have a greater threshold for response. Therefore, dosing requirements
may need to be greater in men than in women for the optimal treatment of glabellar lines. In addition, large patient-to-patient muscle variation in mass, position, frequency of use, and contractile strength requires that dosing and injection sites be adjusted based on clinician judgment and an understanding of proper injection technique to achieve optimal aesthetic outcomes
while minimizing the risk for potential adverse events.
Achieving the desired aesthetic outcome when using BoNTA for the treatment of glabellar lines is more fully optimized when therapy is based on individualized patient assessment incorporating
a thorough understanding of facial anatomy, an objective assessment of muscle mass, and proper injection technique.
Editorial support for this manuscript has been provided by
Craig D. Albright PhD and Robert Gatley MD of Complete Healthcare Communications, Chadds Ford, PA, with funding from Medicis Aesthetics Inc., Scottsdale, AZ.