Intraspinal drug therapy.
Intraspinal drug delivery provides agents directly to their site of action. These sites, receptors within the spinal cord, are bound to a greater degree when drugs are administered intraspinally. The purpose for drug therapy, the acute or chronic nature of delivery, and the drug administration system affect the choice of epidural versus intrathecal route of delivery. Pharmacologic properties, such as solubility, pH, and pKa, aid in dictating the drug chosen for administration. Intraspinal opiates and anesthetics have been used extensively since the 1970s in postoperative, postpartum, and cancer populations. Various delivery systems are in use, including external catheters and implanted ports and pumps. Nursing care includes titration of doses, prevention and management of side effects, and maintenance of delivery systems. Intrathecal baclofen is a new treatment for severe spasticity for patients with multiple sclerosis or spinal cord injury. Candidates include patients who experience persistent spasticity unrelieved by antispasmodics or who experience unacceptable side effects to those oral drugs. Nurses assess spasticity, titrate the intrathecal baclofen to obtain an acceptable degree of spasticity, and manage side effects associated with intrathecal baclofen. A long-term benefit of intraspinal drug delivery, potentially providing benefit to many patients, is the identification of experimental agents that do not cross the blood-brain barrier but prove effective when delivered intraspinally. Pharmacologists and others then might undertake the costly modifications necessary to improve the solubility of the drug. The analogue then might be given orally. "The feasibility of an operation is not an indication for its performance." These words, attributed to the late Lord Cohen, also apply to intraspinal drug delivery. As with any therapy, the simplest and least invasive course should be taken. If, for example, the patient experiences good relief without side effects when given oral opiates or baclofen, there is no good rationale for inserting an intraspinal catheter. The potential for increased morbidity and the escalated expense make this an illogical choice. There are, however, many patients who cannot tolerate oral opiates or baclofen but obtain significant benefit from intraspinal drug delivery. Those who benefit should not be denied this therapy. Much research is necessary as this modality develops. Nurses who comprehend the science of intraspinal drug delivery, as well as the art of patient management, can contribute to this advancing field.