Can TrenibotulinumtoxinE Reverse OnabotulinumtoxinA Effect in Treating Lateral Canthal Lines? (toxin)

Inclusion Criteria:

• Inclusion criteria Adults aged 18 to 65 years. Moderate to severe lateral canthal lines (crow's feet) at maximum smile on both sides, bilaterally symmetrical, as rated by the investigator on the Facial Wrinkle Scale (grade 2 or 3).

Good general health, based on medical history and physical examination. Willing to receive onabotulinumtoxinA in both lateral canthal areas, accept random assignment of trenibotulinumtoxinE or saline to each side, and attend all study visits and photography.

Women of childbearing potential agree to use effective contraception during the study.

Written informed consent.

Exclusion Criteria:

• Any botulinum toxin (any serotype, any site) in the previous 6 months. Known hypersensitivity to any botulinum toxin or to the excipients, or a history of resistance or immunization to botulinum toxin.

Neuromuscular disease (myasthenia gravis, Lambert-Eaton syndrome, ALS, motor neuropathy) or any condition affecting neuromuscular function.

Use of medications that potentiate botulinum toxin (such as aminoglycosides, curare-like agents) in the past 4 weeks.

Facial nerve palsy, eyelid or brow ptosis, marked facial asymmetry, or excessive dermatochalasis.

Deep dermal scarring, or inability to substantially lessen the lines by spreading the skin apart.

Previous surgery of the periorbital area (blepharoplasty, brow lift), or fillers, laser resurfacing, deep peels, or other cosmetic procedures in the periorbital area in the past 6 to 12 months.

Active infection or skin disease at the injection sites. Pregnancy, breastfeeding, or planned pregnancy during the study. Anticoagulant therapy or a bleeding disorder (increased risk of bruising). Participation in another clinical trial within 30 days. Any condition that, in the investigator's opinion, could put the participant at risk or confound the results.