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Introduction Dry mouth is an adverse event reported by cervical dystonia patients treated with botulinum toxin types A and B. It is not clear which serotype (or formulation) leads to the lower incidence of dry mouth: clinical studies comparing serotypes have not been performed and it is inappropriate to compare incidences across separate studies. This study used water consumption in mice treated with either Botox® or NeuroBloc® as a model for the potential incidence of dry mouth in patients. Methods The study comprised three phases: (1) mouse intraperitoneal LD50 assay to confirm potency; (2) mouse hindlimb-paralysis assay to determine the dose-response relationship and paralytic potency; (3) 8-day mouse water-consumption assay using equiparalytic doses of toxins (as determined by assay two) injected into the gastrocnemius muscle. The highest dose chosen for investigation caused marked local toxicity but did not interfere with ability to access drinking water. The lowest dose gave minimal but measurable leg weakness. Investigators were blinded to treatment status. Results (1) Potencies were similar to actual labelled values. (2) Adjusting for measured activity from assay two, the paralytic dose-ratio between Botox® and NeuroBloc™ was 2.23. (3) Daily water consumption in the Botox® groups did not differ from those in the corresponding NeuroBloc™ groups, and neither differed from daily water consumption in control animals. Conclusion Water consumption is similar for mice injected with Botox® and for those injected with NeuroBloc™. This suggests the incidence of dry mouth in patients is unlikely to be different for the two serotypes. [ABSTRACT FROM AUTHOR]