Extended-release Epidural Morphine Formulation Data Far from Clear

Abstract

Washington Hospital Center, Washington, D.C. ivsedation@yahoo.comThe article by Viscusi et al. describing a novel, extended-release epidural morphine formulation is very informative. However, Dr. Viscusi and his coinvestigators have stacked the deck in favor of their study drug by the way they designed their study and presented the data. Their study calls for patients undergoing hip arthroplasty to receive either general or spinal anesthesia; furthermore, median times to first postoperative use of patient-controlled analgesia (PCA) fentanyl were compared. Without knowing who received spinal anesthesia and the duration of the spinal blockade, median times to first postoperative use of PCA fentanyl cannot be interpreted, and neither can the total narcotics use in 24 or 48 h. The study also limited intraoperative use of intravenous fentanyl to 250 μg per patient, clearly an inadequate dose for a hip arthroplasty in the general anesthesia group, and disallowed the use of any other pain medication. By artificially prohibiting the control group from receiving adequate amounts of analgesics, it is no surprise that both surgeons and patients were more satisfied if the study drug, the extended-release epidural morphine, was also administered. Figure 3 of the article shows some patients needing as much as 2,500 μg fentanyl in the first 24 h. Programming intravenous PCA fentanyl, a narcotic not commonly used for postoperative pain control after hip arthroplasty, and limiting the doses at 10–20 μg with a lockout interval of 6 min then can be interpreted as some patients almost constantly pressing their PCA buttons and never achieving adequate pain relief. Extended-release epidural morphine is an interesting formulation; however, it has a higher side effect as demonstrated by 12.5% of patients needing opioid antagonist in the study group versus 0% in the control group. Moreover, it is far from clear from the presented data that it is superior to the present-day pain management of post–hip arthroplasty patients with adequate doses of intravenous PCA morphine plus or minus conventional epidural.Washington Hospital Center, Washington, D.C. ivsedation@yahoo.com