Evolution of dose and response to botulinum toxin A in XXXX : a multicenter study.

@entity1 @entity6389
Botulinum neurotoxin (BoNT) is an effective treatment for @entity6389 ( @entity6389 ). Long-term changes of several variables, including the dose of BoNT, in these @entity1 is largely unknown. We reviewed the clinical charts of 275 @entity1 with @entity6389 treated with BoNT type A (BoNT-A) for at least 5 years since 1989 at ten tertiary centers. The mean dose of BoNT-A per session during the first 5 years of treatment was calculated and the appearance of resistance was noted. The dose of BoNT-A for the whole group showed a significant trend to increase over time (year 1: 180    65 U; year 5: 203    63 U; ANOVA: p < 0.0001). However, when we studied the evolution of the dose of BoNT-A for those @entity1 (n = 49) first injected after 2000 (introduction of current BOTOX preparation in our country), there was no significant increase in dose (year 1: 181.8    75 U; year 5: 181.7    75 U; ANOVA p: ns). A total of 19 @entity1 became secondary nonresponders; all but one of these @entity1 began BoNT-A treatment before 2000. In summary, there is a statistically significant increase of mean dose of BoNT-A per session over time, and this could be explained by the appearance of secondary nonresponders. On the other hand, those @entity1 initially treated after 2000 did not show any statistically significant increase in dose for 5 years. This could be explained by better experience and techniques, fewer immunogenic problems with the current BoNT-A, and also less variability of the dose per vial.
