Long-Term Intrathecal Ziconotide for Chronic Pain: An Open-Label Study

This open-label multicenter study evaluated the long-term safety and efficacy of intrathecal ziconotide and included 78 patients with chronic pain who had completed one of two previous ziconotide clinical trials. Each patient's initial ziconotide dose was based on his or her dose from the study of origin and was adjusted as necessary on the basis of adverse events and analgesic effect. The median ziconotide dose was 6.48 mcg/day (range, 0.00–120.00 mcg/day) at the Initial Visit and ranged from 5.52 to 7.20 mcg/day across all study visits. The most commonly reported new adverse events that were considered ziconotide related were memory impairment (11.3%); dizziness, nystagmus, and speech disorder (8.5% each); nervousness and somnolence (7.0% each); and abnormal gait (5.6%). There was no evidence of increased adverse event incidence at higher cumulative ziconotide doses. Elevations in creatine kinase were noted, but the proportion of patients with creatine kinase elevations did not change from the Initial Visit to the Termination Visit (4.1% each). Stable mean Visual Analog Scale of Pain Intensity scores during the three years of the study suggested no evidence of increased pain intensity with increased duration of ziconotide exposure. Long-term treatment with ziconotide appeared to be well tolerated and effective in patients whose response to ziconotide and ability to tolerate the drug had been previously demonstrated.