Effectiveness and safety of fentanyl compared with morphine for out-of-hospital analgesia.

BACKGROUND

Fentanyl has several potential advantages for out-of-hospital analgesia, including rapid onset, short duration, and less histamine release. Objective. To compare the effectiveness and safety of fentanyl with that of morphine.

METHODS

This was a retrospective before-and-after study of a protocol change from morphine to fentanyl in an advanced life support emergency medical services system in January 2007. Charts from nine months prior to the change and for nine months afterward were abstracted by two reviewers using a standardized instrument. The first three months after the change were excluded. Effectiveness was measured by change in pain scores on a 0-10 scale. A priori-defined adverse events included out-of-hospital events: respiratory rate <12 breaths/min, pulse oximetry <92%, systolic blood pressure <90 mmHg, any fall in Glasgow Coma Scale score, nausea or vomiting, intubation, and use of antiemetic agents or naloxone. Emergency department charts were reviewed for initial pain scores and the same adverse events during the first two hours. Events clearly not attributable to the opioid were discounted. The changes in pain scores were also compared adjusting for confounders by multivariable linear regression.

RESULTS

Three hundred fifty-five patients aged 13 to 99 years received morphine during the nine months before the protocol change and 363 received fentanyl following the washout period. Initial pain scores for morphine (8.1) and fentanyl (8.3) were comparable (95% confidence interval [CI] for difference -1.1 to 0.3). Fentanyl patients received a higher equivalent dose of opioid (7.7 mg morphine equivalents for morphine, 9.2 mg for fentanyl, CI for the difference 0.9 to 2.3). The mean decreases in pain score were similar between the drugs (2.9 for morphine, 3.1 for fentanyl, CI for the difference -0.3 to 0.7). With regard to adverse events, 9.9% of the morphine patients and 6.6% of the fentanyl patients experienced an adverse event in the field (CI for the difference -0.8 to 7.3%). The most common event was nausea, with a rate of 7.0% for morphine vs. 3.8% for fentanyl (CI for the difference -0.1% to 6.5%).

CONCLUSION

Morphine and fentanyl provide similar degrees of out-of-hospital analgesia, although this was achieved with a higher dose of fentanyl. Both medications had low rates of adverse events, which were easily controlled.