Investigator-Based Responder Efficacy and Durability of Botulinum Toxin Type A for Upper Facial Lines: A Timepoint-Specific Analysis of Randomized Placebo-Controlled Trials

Botulinum toxin type A (BoNT-A) is widely used for upper facial lines, but investigator-based responder efficacy and durability across formulations, doses, and assessment methods remain inconsistently reported. In a post hoc analysis of randomized placebo-controlled trials, we evaluated timepoint-specific responder prevalence from clinician assessments at maximum frown and at rest. Four binary responder definitions from ordinal wrinkle severity scales were analyzed separately: none or mild severity (G0–1), ≥1-point improvement, conversion from G2–3 to G0–1, and ≥2-point improvement. Proportions were pooled by random-effects meta-analysis, separately at each reported time point, and for each formulation/dose. Heterogeneity was quantified using I2. Estimates required at least two contributing study arms, and formulations were not compared with one another. At maximum frown, pooled G0–1 prevalence with daxibotulinumtoxinA 40 U was 97% at week 1, 99% at month 1, and 41% at month 6. OnabotulinumtoxinA showed dose-dependent patterns, declining from 95% at week 2 to 8% at month 6 at 40 U, and from 80% at week 1 to 34% at month 4 at 20 U. AbobotulinumtoxinA 50 U declined from 83% at month 1 to 16% at month 6. More restrictive endpoints declined more steeply. At rest, temporal patterns were similar, and the two conditions were not formally compared. Responder prevalence was high early and attenuated substantially by 6 months, with a month 6 prevalence of 41% for daxibotulinumtoxinA 40 U and 8% to 23% for other combinations. These are descriptive formulation-specific observations, not evidence of comparative superiority, because potency units are not interchangeable between products. Timepoint-specific responder reporting is needed in BoNT-A trials.