What must be considered in coadministration of morphine and fentanyl?

Fentanyl is an excellent analgesic choice for rapid control of pain to facilitate splinting and extrication, as its onset of analgesia is almost immediate, and it has less negative effects on blood pressure than morphine. Morphine, however, lasts for longer, and provides analgesic effects within 5 to 10 minutes. Both fentanyl and morphine have been shown to be safe and effective for out-of-hospital analgesia.

Fentanyl is 100 times as potent as morphine, thus co-administration at the maximum doses in the ALS PCS, would be double the recommended opioid dose, causing significant respiratory, cardiovascular and CNS depression risk to the patient. It is, therefore, not recommended. Rather, it is recommended to use multimodal analgesia where possible; i.e. the co-administration of opioids, NSAIDs and acetaminophen.

There are occasions when it may be beneficial to switch between opioids, e.g. from fentanyl to morphine when on a long offload delay, however this requires a patch to the BHP. The purpose of the patch, at RPPEO, is for the paramedic and physician to consult on the positive and negative effects the opioid has had on the patient, and to proceed cautiously with the addition of another opioid. Since analgesia has already been administered and any urgent actions would be completed, the patch is unlikely to be burdensome on the paramedic nor cause delay to patient care.

It may be considered that patients with opioid use disorder who have recently taken opioids are essentially having co-administration if a paramedic administers opioid analgesia. However, these patients typically require higher doses of opioids to achieve analgesia and, therefore, cannot be compared to patients who are opioid naïve. For patient safety, it is best to consult with a BHP before adding opioid analgesics, as is required by the analgesia medical directive.