BACKGROUND AND OBJECTIVES: Voltage-sensitive calcium channel conductance is 
essential for the nervous system to signal a painful event. However, intrathecal 
administration of L-type calcium channel blockers does not provide analgesia. 
The present investigation was designed to assess the safety and analgesic 
efficacy of ziconotide, a new N-type calcium channel blocker, when administered 
intrathecally to patients with acute postoperative pain.
METHODS: This randomized, double-blind, pilot study included patients undergoing 
elective total abdominal hysterectomy, radical prostatectomy, or total hip 
replacement. After intrathecal injection of local anesthetic and before surgical 
incision, a continuous intrathecal infusion of either placebo or 1 of 2 doses of 
ziconotide (0.7 microg/h or 7.0 microg/h) was started and continued for 48 to 72 
hours postoperatively. Primary and secondary efficacy variables were the mean 
daily patient controlled analgesia (PCA) morphine equivalent consumption and 
visual analog pain intensity (VASPI) scores, respectively.
RESULTS: Thirty patients received study drug; 26 were evaluable for efficacy. 
Mean daily PCA morphine equivalent consumption was less in patients receiving 
ziconotide than in placebo-treated patients, and the difference was 
statistically significant between 24 and 48 hours (P = .040). VASPI scores 
during the first 8 hours postoperatively were markedly lower in 
ziconotide-treated than in placebo-treated patients. In 4 of 6 patients 
receiving the high-dose of ziconotide (7 microg/h), adverse events, such as 
dizziness, blurred vision, nystagmus, and sedation contributed to study drug 
being discontinued after 24 hours. After ziconotide discontinuation, these 
symptoms resolved.
CONCLUSIONS: Ziconotide showed analgesic activity, as shown by decreased PCA 
morphine equivalent consumption and lower VASPI scores. Because of a favorable 
trend of decreased morphine consumption with an acceptable side-effect profile 
in the low-dose ziconotide group, 0.7 microg/h may be closer to the ideal dose 
than 7 microg/h. Large-scale studies are required to clarify this issue.