Wallace MS, Kosek PS, Staats P, Fisher R, Schultz DM, Leong M. Phase II, open-label, multicenter study of combined intrathecal morphine and ziconotide: addition of ziconotide in patients receiving intrathecal morphine for severe chronic pain. Pain Med. 2008 Apr;9(3):271–81. doi: 10.1111/j.1526-4637.2007.00355.x. PMID: 18366507.
Phase II, Open-Label, Multicenter Study of Combined Intrathecal Morphine and Ziconotide: Addition of Ziconotide in Patients Receiving Intrathecal Morphine for Severe Chronic Pain