Article Text

Download PDFPDF
Ketamine Potentiates Analgesic Effect of Morphine in Postoperative Epidural Pain Control
  1. Chih-Shung Wong, M.D., Ph.D.*,
  2. Wen-Jinn Liaw, M.D*,
  3. Che-Se Tung, M.D., Ph.D,
  4. Ying-Fu Su, Ph.D and
  5. Shung-Tai Ho, M.D*
  1. *Department of Anesthesiology, National Defense Medical Center and Tri-Service General Hospital, Taipei, Taiwan, Republic of China
  2. Department of Physiology, National Defense Medical Center and Tri-Service General Hospital, Taipei, Taiwan, Republic of China
  3. Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina
  1. Reprint requests: Chih-Shung Wong, M.D., Ph.D., Department of Anesthesiology, Tri-Service General Hospital, #8, Section 3, Tingchow Road, Taipei, 100, Taiwan, Republic of China.


Background and Objectives Ketamine is currently the only N-methyl-D-aspartate receptor channel blocker in clinical use. This study evaluated the analgesic efficacy of epidurally coadministered ketamine and morphine in postoperative pain control.

Methods The patient population consisted of ASA class I and II patients undergoing major joint replacement. Epidural lidocaine was used as the primary anesthesia for the surgery. In phase I of the study, either ketamine (10-30 mg) or morphine (0.5-2 mg) was administered via epidural catheter immediately after surgery. This was done to evaluate the dose-response effect of these drugs when used for postoperative pain relief, and the results were applied to phase II of the study, in which all patients received ketamine pretreatment (total 30 mg) with each dose of lidocaine administered before and during surgery. Forty patients were randomly divided into four groups, each of which received one of three different pain control regimens mixed with 10 mL of saline: group B received 10 mg ketamine, group C 2 mg morphine, and group D 10 mg ketamine plus 0.5 mg morphine while the control group A received 10 mL of saline with no additive. The intensity of pain expressed by patients, as well as the number of intramuscular meperidine (1 mg/kg) injections administered and any side effects that may have occurred, were recorded.

Results Ketamine produced no significant pain relief. A 2-mg morphine dose did produce significant analgesia but was accompanied by a high incidence of side effects. Coadministration of subanalgesic doses of ketamine, 10 mg and morphine, 0.5 mg, however, also produced a strong analgesic effect.

Conclusions Ketamine, although not itself an epidural analgesic agent, potentiates the analgesic effect of morphine, especially when administered as a pretreatment. The resulting lowered dosage of epidural morphine needed for postoperative pain relief reduces, in turn, the incidence of side effects. Pretreatment of patients with ketamine epidurally, followed by injections of combined morphine and ketamine could be a promising new analgesic regimen.

  • ketamine
  • morphine
  • epidural analgesia
  • postoperative pain control

Statistics from

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.


  • Study performed in the Anesthesiology Department of The National Defense Medical Center and Tri-Service General Hospital.

    Supported by the National Council of Science of Taiwan, Republic of China (NSC 83-0412-B-016-022).

    Presented in part at the 7th World Congress of the International Association for the Study of Pain, Paris, France, August 1993.