Statistical Evaluation of the Chemical Stability of Ziconotide Solutions During Simulated Intrathecal Administration

(a) The stability of three ziconotide solutions over time when stored in ziconotide-naïve pumps. The concentration of ziconotide in new, unused Medtronic SynchroMed^® pumps stored at 37°C was expressed as a percentage of the concentration measured at study initiation, and the mean percentage measured each week is displayed for each of three ziconotide solutions: the commercially available 100-mcg/mL formulated solution (diamonds), the commercially available 25-mcg/mL formulated solution (squares), and a 25-mcg/mL ziconotide solution prepared by diluting the commercially available 100-mcg/mL formulation with preservative-free, sterile 0.9% sodium chloride (USP) (triangles). Error bars represent 1 standard deviation below the mean. (b) The stability of three ziconotide solutions over time when stored in pumps that had been previously exposed to ziconotide. Upon completion of the experiments displayed in (a), the Medtronic SynchroMed^® pumps were refilled with a fresh ziconotide solution prepared to match the solution used in the first series of experiments, and the pumps were then stored at 37°C. The concentration of ziconotide is expressed as a percentage of the concentration measured at study initiation, and the mean percentage measured on each sampling week is displayed for each of three ziconotide solutions: the commercially available 100-mcg/mL formulated solution (diamonds), the commercially available 25-mcg/mL formulated solution (squares), and a 25-mcg/mL ziconotide solution prepared by diluting the commercially available 100-mcg/mL formulation with preservative-free, sterile 0.9% sodium chloride (USP) (triangles). Error bars represent 1 standard deviation below the mean.