Botulinum toxin type B (MYOBLOC) versus botulinum toxin type A (BOTOX) frontalis study: Rate of onset and radius of diffusion

BACKGROUND. Botulinum toxin types A and B can improve the appearance of facial wrinkles. Differences in the time until onset and the degree of diffusion have been observed anecdotally, but no direct comparative studies have been done. OBJECTIVE. To compare the rate of onset and the radius of diffusion of botulinum toxin types A and B in the rhytides of the forehead. METHODS. Adults with symmetrical moderate to severe forehead wrinkles at full contracture received botulinum toxin type A (BOTOX; 5 U) on one side of the forehead and type B (MYOBLOC; 500 U) on the other side. Photographs taken at rest and full frontalis contracture were analyzed by computer, and a time-lapse motion picture was created. Radius of diffusion and time until full effect were measured. RESULTS. Botulinum toxin type B had a slightly faster onset of action than type A. All patients responded to type B quickly, whereas some had a delayed response to type A. A greater radius of diffusion was consistently observed with botulinum toxin type B, as measured by the greater area of wrinkle reduction at the doses used. CONCLUSIONS. In this comparative study of patients with symmetrical forehead wrinkles, botulinum toxin type B produced a greater area of diffusion and a more rapid onset of action than type A.