Background: Extending the duration of effect of botulinum toxins—by administering doses beyond those of the approved labels—has been an area of increasing interest in the field of aesthetics.

Objectives: The aim of this study was to investigate the safety and duration of effect of 40-unit (U) prabotulinumtoxinA-xvfs (twice the approved dose and concentration) for the treatment of moderate-to-severe glabellar lines.

Methods: A total of 154 adult patients were randomized 1:1:1 to a single treatment of either 40 U prabotulinumtoxinA-xvfs (PRA 40, 5 injections of 8 U/0.05 mL), or 20 U of either prabotulinumtoxinA-xvfs (PRA 20) or onabotulinumtoxinA (ONA 20). Both 20-U controls were administered as 5 injections of 4 U/0.1 mL. Efficacy and safety were assessed on days 2, 7 (by telephone), 30, and every 30 days thereafter up to 365 days or until the patient had returned to baseline. The primary effectiveness endpoint was the duration of effect (estimated by Kaplan-Meier analysis), defined as the number of days from treatment day (baseline) to the day that glabellar line severity at maximum frown by investigator assessment returned to the baseline value.

Results: Patients had a mean age of 47 years (20-72 years); 69.5% had severe glabellar lines at baseline. Of the 36 adverse events, 32 (88.9%) were mild and 4 (11.1%) were moderate in severity; none were serious. The median durations of effect were estimated to be 183, 149, and 148 days for PRA 40–, PRA 20–, and ONA 20–treated patients, respectively.

Conclusions: In this phase 2 pilot study, 40 U prabotulinumtoxinA-xvfs was observed to be safe and had a duration of 6 months.

Keith A. Marcus MD

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