INTRODUCTION: The standard application of botulinum toxin for frontal wrinkles is at the intramuscular level. Some authors have suggested that the combination with intradermal application can bring about a more natural result, avoiding the paralyzing effect of the intramuscular application only. Objective: Establish if the paralyzing effect of type A onabotulinum toxin in the forehead, applied intradermally, is as effective as of the same toxin applied intramuscularly after: 48 hours, one, two, four, eight and 12 weeks for the treatment of frontal wrinkles.
MATERIAL AND METHODS: Sixteen patients with frontal wrinkles were randomized to receive intramuscular or intradermal onabotulinum toxin and were reevaluated after 48 hours, one and two weeks, one, two and three months.
RESULTS: Data were collected from 16 patients. Mean age was 33 years (standard deviation 5.96). Paralysis occurred in 93.3% in the intramuscular side and in 53.5% in the intradermal side in two weeks (p= 0.07). Median pain grade was 2.69 in the intramuscular side and 4 in the intradermal side (p=0.072).
CONCLUSIONS: Despite the highest frequency of the presence of paralysis in the intramuscular side in all evaluations, there was no statistically significant difference between the sides.

Keywords: Botulinum toxins type A; Injections, intradermal; Injections, intramuscular