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.