Phase IV study comparing incobotulinumtoxinA and onabotulinumtoxinA using a 1:1.5 dose-conversion ratio for the treatment of glabellar frown lines
Correspondence: W Prager, MD, Dermatologikum, Stephansplatz 5, 20354 Hamburg, Germany. E-mail: firstname.lastname@example.org
IncobotulinumtoxinA and onabotulinumtoxinA are effective treatments for glabellar frown lines, and a dose of 20 U is recommended for both preparations. However, debate continues over using the same dosages of these products, although a 1:1 dose ratio has been proven in several head-to-head clinical trials in neurological and esthetic indications.
To investigate whether a 50% higher dose of onabotulinumtoxinA was nonsuperior to incobotulinumtoxinA in the treatment of glabellar frown lines in the short and long term.
Methods and materials
Subjects aged 18–65 years with symmetrical moderate-to-severe glabellar frown lines (score: ≥2 on a validated Merz 5-point scale) at maximum frown were enrolled. Corrugator muscles on both sides were treated with two injections of either 4 U incobotulinumtoxinA or 6 U onabotulinumtoxinA (equivalent to 20 and 30 U, respectively, if corrugator muscles on both sides and the procerus are treated) allowing intra-individual comparison. Glabellar frown line severity was assessed from standardized photographs every 4 weeks for 4 months and, in a subset of subjects, for up to 6 months posttreatment. The primary efficacy endpoint was the percentage of subjects with an improvement of ≥1 point on the 5-point scale at week 4. Nonsuperiority was assessed by comparing the response rates of each product.
Nonsuperiority of a 50% higher dose of onabotulinumtoxinA to that of incobotulinumtoxinA was confirmed at 4 weeks, 4 months, and 6 months posttreatment.
There is generally no reason to increase the dose of either incobotulinumtoxinA or onabotulinumtoxinA above the 20 U recommended for glabellar frown lines.