A COMPARISON OF THE SPREAD OF 3 FORMULATIONS OF BOTULINUM NEUROTOXIN-A AS DETERMINED BY EFFECTS ON MUSCLE FUNCTION

The purpose of these experiments was to compare the spread of three fo rmulations of botulinum neurotoxin A. A gelatin/phosphate buffer (C), Dysport(R) (D {0.5 U}, Botox(R) (B {0.167 U}), or a purified preparati on of botulinum neurotoxin A [Bont A] (BA {0.5 U}) was injected into t he tibialis anterior of male, Wistar rats. After 4 days, the adjacent extensor digitorum longus muscle was isolated in situ and the nerve wa s maximally stimulated to determine contractile properties and the rat e of fatigue. There were no differences in body or muscle weights betw een any of the groups after 4 days of treatment. Maximal twitch and te tanic tensions were decreased approximate to 25% (p < 0.05) in all tre atment groups compared to C. In addition, rate of tension development was significantly less in all treatment groups compared to C but one-h alf relaxation time and time to peak tension were not different betwee n any groups. Fatigue of the muscle was significantly faster in all gr oups compared to C but there was no difference between treatment group s. These data indicated that botulinum toxin A injected intramuscularl y was likely to spread to adjacent muscles but that the spread was not different between the three formulations tested. The effect of the sp read ranged from a slight to a severe reduction in maximal tension but this did not occur in all animals studied. (C) 1998 Rapid Science Ltd .