This invention provides injectable compositions comprising botulinum toxin that may be administered to a subject for various therapeutic, aesthetic and/or cosmetic purposes. The injectable compositions embraced by the invention exhibit one or more advantages over conventional botulinum toxin formulations, including reduced antigenicity, a reduced tendency to undergo unwanted localized diffusion following injection, increased duration of clinical efficacy or enhanced potency, higher responder rates, faster onset of clinical efficacy, and/or improved stability. According to the invention, single treatment of the compositions by injection affords significant clinical responses and at least a 26-week duration of effect in a subject undergoing treatment, as provided by the described treatment methods, as well as still higher responder rates and/or longer duration of effect following subsequent treatments.
