Evaluation of the efficacy and safety of botulinum toxin type A to induce temporary ptosis in dogs.

PURPOSE To verify the safety and efficacy of botulinum toxin type A (BoNT/A) to promote protective ptosis in dogs. METHODS In this prospective interventional study, a total of 10 dogs underwent transcutaneous anterior chemodenervation of levator palpebral superioris with 15 U of BoNT/A. The systemic changes, ocular mobility, visual function, intraocular pressure (IOP), tear production, and the onset, degree, and duration of ptosis were evaluated on a daily basis during the first 7 days and on days 14, 21, and 28 after application. RESULTS The onset of the clinical effect was observed between 2 and 3 days after application of the toxin; the time taken for maximum ptosis to develop varied from 4 to 7 days (mean 5 days) and the average duration of the toxin effect was 21 days. The mean percentage reduction in palpebral fissure height was 42.859% (SD±35.714%-59.821%). There was not a statistically significant difference in IOP before and after the BoNT/A application (P=0.974), or lacrimal production evaluation (P=0.276). There was no change in ocular mobility and no other adverse effect was observed in association with the administration of the study drug. CONCLUSION The application of BoNT/A into the levator palpebral superioris muscle in dogs was effective and safe to promote protective ptosis with a temporary covering of the cornea.