The purpose of this study is to understand the effects of intrathecal ziconotide (an experimental pain medication) when the dose is slowly increased over a 3-week period in patients with severe chronic pain. During the weaning phase, the study will also gather information about switching from other intrathecal or IT medication (slowly pumped directly into the space around the spine) to other systemic pain medication (by mouth or through the skin using a patch). After being weaned off current IT medication, patients will be placed on IT ziconotide or placebo (non-active substance) as well as being allowed a stable dose of systemic pain medications.

Patients who complete this study may be eligible for long-term ziconotide therapy via extension protocol ELN92045-352.

Inclusion Criteria:

• Patient is able to read, understand, and voluntarily sign the Institutional Review Board (IRB) approved, written informed consent document prior to the performance of any study-specific procedures;
• Patient must be male or female at least 18 years of age;
• Patient must have severe chronic pain for whom IT therapy is warranted;
• Patient must be willing and able to comply with the protocol, and able to maintain the Patient Daily Diary for Opioid Consumption;
• Patient must have an implanted programmable SynchroMed® Infusion System in place for the treatment of chronic pain;
• Female patients of childbearing age agree to use adequate, appropriate contraceptive methods.

Males and their partner(s) of childbearing age must use adequate, appropriate contraceptive methods.

Exclusion Criteria:

• Patient is pregnant or lactating;
• Patient has been on an investigational drug other than ziconotide or device within 30 days prior to the initiation of the study drug;
• Patients with a known hypersensitivity (allergy) to ziconotide or any of the excipients (other compounds) in the formulation;
• Patient has a condition that would contraindicate the use of IT analgesia, including the presence of infection at the microinfusion injection site (where the needle is inserted in your abdomen to fill the pump with medication), uncontrolled bleeding diathesis (tendency for bleeding) and spinal canal obstruction that impairs circulation of Cerebral Spinal Fluid.