title: Chemical Stability of Admixtures Combining Ziconotide with Morphine or Hydromorphone During Simul ated Intrathecal Administration.
abstract: Objective.  To determine the stability of admixtures combining ziconotide with morphine or hydromorphone under simulated intrathecal infusions. Materials and Methods.  Admixtures of ziconotide (25 µg/mL) with morphine or hydromorphone (both at 35 mg/mL) were stored in Medtronic SynchroMed® II pumps at 37°C, and in control vials at 37°C and 5°C. Drug concentrations were determined using high-performance liquid chromatography. Results.  The ziconotide pump concentration with morphine declined to 79% of initial in 17 days, and to 88% of initial after 25 days with hydromorphone. Ziconotide concentrations in control vials stored at 37°C displayed similar rates of decay, but vials stored at 5°C exhibited no ziconotide loss. A statistical evaluation of the two combinations shows ziconotide-hydromorphone retaining 80% stability for 40 days (extrapolated), compared to 15 days for ziconotide-morphine. Morphine and hydromorphone were stable in the presence of ziconotide under all conditions. Conclusions.  Ziconotide-hydromorphone admixtures were more stable than ziconotide-morphine admixtures.
authors.affiliation: Elan Pharmaceuticals, Inc, South San Francisco, California; and              Gilead, Inc, Foster City, California, USA.
authors.forename: David
authors.initials: D
authors.lastname: Shields
authors.forename: Rick
authors.initials: R
authors.lastname: Montenegro
authors.forename: Matthew
authors.initials: M
authors.lastname: Ragusa