Opioid intraspinal

Opioids maybe administered in a variety of routes including oral (tablet and liquid), sublingual, rectal, transdermal, transmucosal, intravenous, subcutaneous, and intraspinal. While the oral and transdermal routes are most common, the method of administration is based on patient needs (severity of pain) and characteristics (swallowing difficulty and preference). Oral opioids have an onset of effect of 45 minutes, so intravenous or subcutaneous administration maybe preferred if more rapid relief is desired. Intramuscular injections are not recommended because of pain at the injection site and wide fluctuations in drug absorption and peak plasma concentrations achieved. More invasive routes of administration such as PCA and intraspinal (epidural and intrathecal) are primarily used postoperatively, but may also be used in refractory chronic pain situations. PCA delivers a self-administered dose via an infusion pump with a preprogrammed dose, minimum dosing interval, and maximum hourly dose. Morphine, fentanyl, and hydromorphone are commonly administered via PCA pumps by the intravenous route, but less frequently by the subcutaneous or epidural route. 

Data from American Pain Society. Prinaples of Analgesic Use in the Treatment of Acute Pain and Chronic Cancer Pain, 5th ed. Glenview, IL American Pain Society, 2003 and Ready BL. Regional analgesics with intraspinal opioids. In Loeser JD, Butler SH, Chapman CR, etal, eds. Bonica s Management of Pain. Philadelphia Lippincott Williams 8 Wilkins, 2000 1953-1966. 

Pruritus is a common and potentially disabling complication of opioid use. It can be caused by intraspinal or systemic injections of opioids, but it appears to be more intense after intraspinal administration. The effect appears to be mediated largely by dorsal horn neurons and is reversed by naloxone. 

Analogous to the relationship between systemic opioids and NSAIDs, intraspinal narcotics often are combined with local anesthetics. This permits the nse of lower doses of both agents. 

Skin Pruritus, a common adverse effect related to opioid use, affects psychosocial well-being. The hterature on the pathogenesis of opioid-induced pruritus is hmited, and treatment options for this condition remain largely unsatisfactory [48 ]. The associated susceptibility factors include epidural or intraspinal administration, higher doses of opioids, parturients, and intrathecal morphine administration. 

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