Prospective Open-Label Study of Botulinum Toxin Type B (Myobloc) at Doses of 2,400 and 3,000 U for the Treatment of Glabellar Wrinkles

BACKGROUND: A previous open-label study evaluated botulinum toxin type B (BTX-B; Myobloc) for the treatment of glabellar wrinkles and showed that it is safe and effective at a dose of 1,800 U. The duration of effect at this dose was approximately 8 weeks, and it was felt that higher doses would result in a longer duration of effect. OBJECTIVE: This is a prospective open-label study to assess the safety, efficacy, and duration of response following BTX-B injection at doses of 2,400 and 3,000 U for the treatment of glabellar frown lines. METHODS: A total of 39 patients were enrolled: 16 patients received 2,400 U. Eighteen patients received 3,000 U, and 5 patients received saline injections (control group). Doses were divided equally among six sites. RESULTS: All subjects had rapid improvement of interglabellar rhytides, with full response seen within 2 to 3 days. The duration of effect was 9.6 and 10.4 weeks with 2,400 and 3,000 U, respectively. Five subjects (two in the 2,400-U group and three in 3,000-U group) reported adverse events related to the BTX-B injection. Three subjects complained of mild pain at the injection site, and two subjects complained about lid droop/ptosis (one with the occurrence of headache). CONCLUSIONS: BTX-B injection is safe and effective for the treatment of glabellar wrinkles. It has a very rapid onset of action, and increasing the dose appears to prolong the duration of response. At 3,000 U, the duration of response was 10.4 weeks and was associated with minimal adverse effects. Adverse events were mild and were similar to those seen in previous studies with BTX-A. Additional studies evaluating BTX-B at higher doses are recommended to prolong the duration of response in the treatment of glabellar wrinkles.