the frontalis activity measurement standard a novel contralateral method for assessing botulinum neurotoxin typea activity background there are conflicting data regarding the specific attributes of botulinum neurotoxin typea bonta products including onset of action duration and spread because accurate objective methods for assessing their clinical activity are lackingobjective to refine definitions for bonta activity utilizing the frontalis muscle and describe the frontalis activity measurement standard fms an objective method for measuring changes in frontalis muscle activity as a metric for assessing bonta pharmacodynamicsmethods as part of a study to assess bonta activity 20 subjects with severe frontalis lines at maximum elevation were injected with two bonta products at five points on contralateral sides of the frontalis changes in maximum baseline frontalis elevation were measured by a blinded investigator using the previouslyvalidated frontalis rating scale frs and the fms frontalis activity endpoints were redefined to include initial full and complete onsets of action and partial full and complete efficacyresults differences in the onset of effect of the bonta products were detected with both the frs and fms however the fms detected changes in frontalis activity earlier than the frs a significant correlation between the frs and fms was documentedconclusion the frontalis muscle activity allows for enhanced assessment of bonta activity and attributes the fms appears to be a sensitive and objective tool for measuring pharmacodynamic parameters of bonta refining definitions of bonta activity provides a more accurate means for describing the clinical effects of bonta