Botulinum toxins types A and B for brow furrows: preliminary experiences with type B toxin dosing.

Background: Facial lines resulting from hyperactivity can be misleading manifestations of negative emotions, fatigue and stress. They may also contribute to a perception of facial aging. A well established treatment is botulinum toxin type A (BTX-A). Recently, botulinum toxin type B (BTX-B) has become available for the treatment of cervical dystonia. There has been little comparison on the efficacy of the two different types of botulinum toxins, nor is there information on appropriate dosing of BTX-B for facial muscles.

Objectives: The purpose of this pilot study was to observe the effects of BTX-B in comparison to BTX-A, on patients with brow furrows assessing initial efficacy and duration of effect.

Methods: Patients were injected with BTX-B in two different dose conversions against BTX-A to the corrugator-procerus complex. Some patients received a conversion of 50 units of BTX-B (total of 1000 units) to one unit of BTX-A while others received a conversion of 100 units of BTX-B (total of 2000 units) to one unit of BTX-A. The patients treated with BTX-A received a total of 20 units. These patients were clinically assessed prior to treatment and 3 days, 1 week, 4 weeks, 12 weeks and 16 weeks after treatment.

Results: Both types of botulinum toxin were effective at improving glabellar frown lines. The onset of actions occurred slightly sooner (2-3 days) with BTX-B than with BTX-A (3-7 days). Duration of effect with BTX-A was at least 16 weeks. With 1000 units of BTX-B, dose duration was 6-8 weeks and with 2000 units of BTX-B, duration was 10-12 weeks.

Summary: Both types of botulinum toxin are effective at correcting deep glabellar furrows. At least with the doses used, BTX-B has a quicker onset of action and BTX-A has longer benefit for glabellar wrinkles. These data strongly suggest that further dose ranging studies of BTX-B are necessary and indicated in controlled double blind studies in a larger patient population.