Biodegradable neurotoxin implants and methods of making and using such implants are provided. Biodegradable neurotoxin implants include a neurotoxin, a biodegradable polymer component, and an acidity regulating component. The biodegradable polymer component is effective in controlling the release of the neurotoxin from the implant when the implant is located in a patient's body. The acidity regulating component is effective in maintaining a pH of the implant in a desired range that may be effective in stabilizing the neurotoxin as the implant biodegrades when the implant is located in a patient's body. In one embodiment, an implant includes a botulinum toxin, a biodegradable polymer, and either monomers from which a biodegradable polymer is derived or oligomers including monomeric units substantially identical to a monomer from which a biodegradable polymer is derived, or a combination of such monomers and oligomers. The oligomers and biodegradable polymer may be derived from a single type of monomer. The implants disclosed herein may be administered to a human or animal patient in which a therapeutic effect is desired for prolonged periods of time.