Onabotulinumtoxin Type A Dosage for Upper Face Expression Lines in Males: A Systematic Review of Current Recommendations.

[BACKGROUND] Botulinum toxin injection is the most commonly performed minimally invasive aesthetic procedure in men. Despite various recommendations by experts on the use of onabotulinumtoxin type A in the literature, distinct guidelines for its use in males and females do not exist.

[OBJECTIVES] The aim of this study was to delineate safe and effective doses for the use of onabotulinumtoxin type A in males for correction of upper facial expression lines.

[METHODS] PubMed (MEDLINE), Embase, the Cochrane database, and Google Scholar were searched from 2002 to 2019 inclusive. Three researchers independently assessed trials for inclusion, extracted data, checked for accuracy, and assessed the evidence with AGREE II.

[RESULTS] Average dosing recommended for the treatment of upper face expression lines was specific to glabellar frown lines, crow's feet, and horizontal forehead lines. Changing trends and gender variation was noted in each of the studies. Six of the 11 recommendations suggest the need to alter dosing in male patients, although do not give separate recommendations.

[CONCLUSIONS] There is an urgent need for up-to-date recommendations for the use of onabotulinumtoxin type A in upper face expression lines of male patients.