To the Editor:—
We commend the work of Dougherty and Staats, 1which provides an update for the reader regarding pending advances in intrathecal drug therapy for chronic pain. We also commend their effort to provide us with a view of therapeutic horizons in chronic pain management. Their review, however, may not be completely accurate about the status of intrathecal morphine in the treatment of chronic pain.
The authors state that morphine is the “gold standard” for intrathecal drug administration because it has been approved for “long-term” intrathecal treatment of pain by the United States Food and Drug Administration. The Physician’s Desk Reference 2reflects the Food and Drug Administration’s position on intrathecal morphine (Duramorph; Elkins-Sinn, Cherry Hill, NJ). The 1999 Physician’s Desk Reference states that “Repeated intrathecal injections of Duramorph are not recommended.” Furthermore, the Physician’s Desk Reference states that if pain recurs after single intrathecal injection, “alternative routes of administration should be considered, since repeated doses of morphine by the intrathecal route is limited.” The Physician’s Desk Reference has no comment about the safety and effectiveness of intrathecal morphine for long-term constant infusions.
The authors also state that long-term intrathecal morphine “has fewer side effects than do systemic opioids.” To substantiate their claim, the authors cite eight reports. However, none of these reports compare long-term systemic morphine with long-term intrathecal morphine in well-controlled trials in patients with chronic pain.
It is well-recognized that a single injection of morphine into the intrathecal space produces a selective pain-blocking effect on the spinal cord, sparing the patient many of the serious side effects caused by morphine when it is administered orally (e.g. , sedation). 3Soon after this discovery, enthusiasm developed to implant permanent morphine pumps to treat non–cancer-related chronic pain, especially after Medicare began to approve this surgical procedure for reimbursement. Implantation of a morphine pump is a relatively invasive and expensive treatment modality. 4Despite almost 20 yr of testing, no well-controlled studies have emerged that indicate that long-term use of the morphine pump offers an advantage over oral morphine for treating various chronic pain syndromes. In fact, many patients with the implanted morphine pump are prescribed oral opioid at the same time. The same complications sometimes associated with oral morphine use are found with the morphine pump, such as development of drug tolerance, nausea, constipation, weight gain, decreased sexual desire (libido), swollen legs (edema), and increased sweating. 5,6In addition, malfunction of the pump system (dislodgment of the catheter) or surgical complications may present a significant problem. 6
In the era of managed care, our strength as a specialty will depend more and more on our willingness to compare safer and more cost-effective therapeutic options with anesthetic procedures in well-controlled clinical trials.