Repeated onabotulinum neurotoxin A injections for drooling in children with neurodisability.
Stijn Bekkers, Theresa Ys Leow, Karen Van Hulst and 3 others
PMID 33772779WHAT IT FOUND
Repeated onabotulinum toxin A injections for drooling remained effective but showed a significantly smaller reduction in drooling after the second and third injections compared to the first.
Treatment success dropped from 74% after the first injection to 41.6% after the second.
Key findings
01The reduction in drooling severity was significantly smaller after the second injection compared to the first, for both objective and subjective measures.
02Clinically meaningful treatment success rates declined from 74.0% after the first injection to 41.6% after the second, before rising slightly to 45.8% after the third.
03No serious adverse events were reported, and the overall frequency of adverse events did not differ significantly between injections.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study was retrospective and clinically driven, meaning children who responded well were more likely to continue treatment, introducing survivor bias that may overestimate the effect of later injections. The number of children receiving a third injection was small (24), limiting the statistical power to detect changes in efficacy at that stage. Data on previous botulinum toxin treatments for other indications (e.g., spasticity) were not thoroughly assessed, which could have influenced the development of neutralizing antibodies and treatment response. The definition of treatment success was dichotomous (50% reduction), which may not capture clinically relevant nuances in partial responders.
Declared interests
The paper does not explicitly state funding sources or author conflicts of interest in the provided text, but notes the study was supported by non-U.S. government sources.
The easy way to misread this
Do not interpret the lower baseline drooling levels before subsequent injections as evidence that the treatment is becoming less necessary; the reduced effect size and lower success rates indicate a diminishing response to the toxin itself, not just a change in the child's condition.