Pain management with spinally administered opioids.

The use of spinally administered opioids to manage pain is discussed. Central action on opioid receptors of the substantia gelatinosa allows opioids to be administered spinally for pain originating anywhere inferior to the cranial nerves. Spinal opioids are most commonly administered for intractable midline sacral and perineal pain. The best candidates for spinal opioids are patients in whom appropriate "conventional" therapy no longer provides adequate relief, patients who experience severe adverse effects from conventional therapy, and patients for whom alternative anesthetic procedures are inappropriate or have failed. A reasonably safe initial dose is morphine sulfate 1 mg intrathecally. The availability of preservative-free, concentrated morphine sulfate enables larger doses to be safely and comfortably administered. Increased dosage requirements may result from tolerance, progression of disease, increased systemic absorption, or slippage of the catheter tip. As with systemically administered opioids, care must be exercised when discontinuing spinal opioid therapy. Adjuvant drugs used with spinal opioids include systemically administered analgesics, antidepressants, corticosteroids, and spinal local anesthetics. The administration of spinal opioids with systemic opioids or other CNS depressants may result in excessive sedation, respiratory depression, nausea, vomiting, constipation, pruritus, and other adverse effects. Spinally administered opioids can be used to manage severe chronic pain effectively, safely, and comfortably.