• David Shields, Rick Montenegro, and Jennifer Aclan.
• Elan Pharmaceuticals Inc., South San Francisco, CA, USA; Gilead Inc., Foster City, CA, USA.
• Neuromodulation. 2007 Oct 1;10 Suppl 1:12-7.

AbstractObjective.  To determine the stability of admixtures combining ziconotide with commercially formulated or powdered baclofen during simulated intrathecal infusion under laboratory conditions at 37°. Materials and Methods.  Admixtures of ziconotide (25 µg/mL) with commercially formulated (1.5 mg/mL) or powdered (2.0 mg/mL) baclofen were stored in implantable intrathecal pumps at 37°. Drug concentrations were determined with high-performance liquid chromatography, and the length of time that the concentrations of both drugs remained ≥90% and ≥80% of initial (ie, the 90% and 80% stability, respectively) was estimated based on lower 95% confidence bounds obtained via linear regression. Results.  Baclofen was stable in both admixtures. In the commercially formulated baclofen admixture, the mean ziconotide concentration declined to 82.2% of initial in 30 days; the estimates for 90% and 80% stability were 12 and 29 days, respectively. In the powdered baclofen admixture, the mean ziconotide concentration declined to 87.4% of initial in 30 days; the estimates for 90% and 80% stability were 20 and 41 days, respectively. Conclusion.  Ziconotide-baclofen admixtures were more stable when prepared using powdered baclofen rather than a commercial baclofen formulation.

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