[The pharmacologic basis of postoperative pain therapy.  Epidural opioid administration]. 
The administration of epidural opioids is alternatively used in the management of postoperative analgesia.  However, the administration is associated with side effects, including respiratory depression, somnolence and pruritus.  A rational opioid selection between the hydrophilic and lipophilic opioids morphine, hydromorphone, alfentanil, fentanyl and sufentanil is discussed in this mini-review.  Thus, the administration of the lipophilic opioid sufentanil might has some advantages.  Notwithstanding, epidural opioid administration alone offers no marked clinical advantages compared to the intravenous route.  In future, reduced doses of lipophilic opioids and local anaesthetics like bupivacaine 0.05-0.1% may provide benefits over the use of either drug alone and may offer marked clinical advantages over the intravenous route of opioids alone.  The same holds true for alpha 2-adrenoceptor agonists as adjuvants.  However, multicenter dose-ranging studies are necessary to determine both the ideal concentrations of the drug combinations and the general outcome.  Moreover, we must also determine cost effectiveness for our postoperative analgesic techniques.