الفهرس 
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Abstract
The epidural administration of opioids is currently being investigated for relief of pain. Epidural administration of morphine sulphate has provided, long lasting relief for postoperative or chronic pain. The major advantages of selective blockage of pain by spinal opioids lie in the absence of sympathetic blockage and neuromuscular blockage allowing easy ambulation of patients and avoidance of cardiovascular collapse or convulsions, the major complications of local anesthetic blockage. Opioids administered IV or IM for postoperative pain relief, the parturient induce potential side effects, including respiratory depression, nausea, vomiting, orthostatic hypotension, delayed gastric emptying and diminished uterine activity in parturients and placental transfer of the drug resulting in neonatal respiratory depression. If intrathecal or epidural opioids always provide safe and effective analgesia for labor, these techniques would offer distinct advantages over current analgesic methods. There would be no motor block, no sympathectomy and in small doses no neonatal effects.
Epidural administered opiates must initially cross the dura mater before exerting their effect in the substantia gelatinosa (Rexed’s lamina II – III). These agents are also subject to uptake epidural plexus of veins. Uptake and distribution into plasma after epidural administration resembles that seen after intramuscular injection. The portion of the drug that is not taken in the vascular compartment is available to cross the dura. Hydrophilicity determines how much drug will cross the dura.