The purpose of this study is to evaluate if the effect of ziconotide can be tested by intrathecal bolus doses.

The intrathecal route for administration of analgesia has been in use in clinical practice for the last 3 decades. It is recommended to trial the patient with intrathecal drug therapy prior to implanting an intrathecal drug delivery device. Trials can be performed using a single bolus injection or by a continuous intrathecal infusion administered through an external catheter. Ziconotide has been approved by EMA for the treatment of chronic severe pain in 2005. So far trials of ziconotide have largely been conducted using external catheters with the drug administered by intrathecal infusion over a number of weeks. Infusions trials have been shown to be expensive, associated with a risk of meningitis and inconvenient to both patient and physician. The option of conducting a trial of intrathecal ziconotide therapy by bolus injection remains unexplored.

This study aims to evaluate the efficacy and safety of a bolus dose of ziconotide (Prialt®) to evaluate the option of continuous administration of the drug via implanted pump in the event of a successful trial.

Inclusion Criteria:

• Patient, at least 18 years of age
• suffering from severe chronic (≥ 6 months) pain, who has failed on conventional pharmacological treatment
• only patients with peripheral neuropathic pain or central neuropathic pain, due to trauma or surgery, will be included
• Average usual VASPI last week ≥ 40 mm
• Patient capable of judgment, i.e. able to understand information regarding the drug, the mode of administration and evaluation of efficacy and side effects Signed informed consent

Exclusion Criteria:

• Limited life expectancy (investigator's judgement)
• Intrathecal chemotherapy
• Known or suspected intracranial hypertension
• Known liver or kidney disease, defined as ASAT, ALAT, Total Bilirubin, ALP or S- Creatinine > 1.2 x ULN
• Advanced cardio-pulmonary disease (investigator's judgment)
• Ongoing infection, whether systemically or locally in the lumbar area
• Coagulopathy (including medication with warfarin, clopidogrel and heparin)
• Allergy to ziconotide or any of the excipients in the ziconotide vial
• History of psychiatric disorders which in the investigator's opinion would put the patient at risk
• Pregnant or lactating woman.
• Menstruating women must use an effective contraceptive method (contraceptive pill or intrauterine spiral) during the trial period