Cancer pain control has been reported in both anecdote and uncontrolled series using both bolus and continuous techniques of epidural and intrathecal morphine delivery. Comparative analgesic efficacy and duration of pain control in similar cancer pain syndromes using conventional narcotic therapy and chronic intraspinal morphine is unknown. Suggested but untested advantages of intraspinal morphine include effective analgesia when oral narcotics fail, decreased total narcotic use, improved congnitive and psychomotor function, and decreased neurodestructive procedures for pain control. Continuous intratecal or epidural infusion via implanted reservoir has the potential advantages of decreased injections over percutaneous epidural narcotic, reduced infection and respiratory complications, potential delivery of alternate intraspinal analgesics, and patient convenience; percutaneous epidural techniques are less expensive, entail less surgery and offer self control and simplicity. All techniques are limited by apparent tachyphylaxis to morphine analgesia. Newer strategies, though untested, suggest tolerance may be minimized, and thus cancer pain control reestablished, by use of alternate intrathecal or epidural drugs. Thus, work is needed to 1) document comparative analgesic and functional outcomes and tolerance development in conventional therapy versus chronic percutaneous epidural or implanted pump delivered intrathecal morphine; 2) to develop and test new drugs and strategies to combat spinal narcotic tolerance. Our purpose is to: 1) continue outpatient accrual for comparison of cancer pain control (analgesic efficacy, functional status, cognitive function) in stratified populations with similar regional cancer pain syndromes (pain below diaphragm group plus pain above diaphragm) with similar baseline narcotic requirements using a) continuous intrathecal morphine or b) an experienced oncology service using conventional narcotic regimens, and after accrual of 20 patients in both a and b, c) to compare chronic percutaneous epidural morphine with a and b; 2) establish pharmacokinetic and pharmacodynamic characteristics of intrathecal morphine, hydromorphone, and clonidine in prospective alternate intrathecal agents in cancer pain patients; 3) document both adverse effects of intrathecal analgesics on spinal cord function (serial somatosensory evoked potentials) and gross histopathology of spinal cord; and lastly 4) to employ chronic intrathecal canine and rat models to develop and test new drugs and strategies for ameliorating spinal narcotic tolerance in order to restore pain control and reduce need for neuroablative cancer pain procedures.
