The side effects of morphine and hydromorphone patient-controlled analgesia

Abstract

Background: Despite "clinical lore" among health care providers that treatment with hydromorphone results in improved pain control and fewer adverse side effects, morphine continues to be the first-line medication for postoperative patient-controlled analgesia (PCA). In this study, we compared the efficacy and side-effect profiles of morphine and hydromorphone at concentrations producing equivalent drug effect measured by pain score and miosis.

Methods: We conducted a prospective, randomized, double-blind trial of 50 general and gynecological surgery patients. Subjects were randomly assigned to receive either morphine (1 mg/mL) or hydromorphone (0.2 mg/mL) via PCA after surgery and were followed for a period of 8 h. The primary outcome was nausea. Secondary outcome variables were pruritus, vomiting, sedation, pain report, pupillary miosis, and patient satisfaction.

Results: The side effect profile was not different between drugs. The incidence of nausea did not differ between morphine and hydromorphone-treated patients (1 h: 44% vs 52%, 8 h: 68% vs 64%), vomiting (1 h: 4% vs 0%, 8 h: 0% vs 4%), or pruritus (1 h: 4% vs 16%, 8 h: 40% vs 40%). There was no difference in the amount of medication required to treat side effects or patient satisfaction. The average ratio of morphine to hydromorphone use was about 7:1. The patients used 10.9+/-6.0 mg morphine versus 1.57+/-1.0 mg hydromorphone after 1 h and 29.0+/-18.0 mg morphine versus 3.9+/-2.5 mg hydromorphone after 8 h. There was no difference between the morphine and hydromorphone groups with respect to postoperative pain scores with movement at 1 h (7.9+/-2.3 vs 7.1+/-2.4) or 8 h (5.7+/-2.8 vs 5.9+/-2.7). There was also no difference in pain at rest or miosis between groups.

Conclusions: We found no systematic difference between morphine and hydromorphone in opioid-related side effects. Neither was there any difference in efficacy of pain control or patient satisfaction when patients self-titrated to equal drug effect as measured by equianalgesia and pupillary miosis. The choice between morphine and hydromorphone for use in PCA should be guided by patient history, as there may be idiosyncratic reactions to either drug.