A thermo-reversible thermoplastic pharmaceutical composition, comprising a botulinum toxin and a biocompatible poloxamer which provides thermoreversibility to the composition and additionally stabilizes the botulinum toxin, is described. The pharmaceutical composition can be administered to a patient as a liquid, and gels after administration into a sustained release drug delivery system from which the biologically active botulinum toxin is released over a multi-day period thereby localizing the drug as a depot and controlling release to enhance the therapeutic effect per dose.