Objective. We observed that parenteral morphine is routinely prescribed in doses that are quite low in relation to doses of alternative parenteral opioids and in comparison with published effective doses and guidelines. The present study was undertaken to determine: 1) whether different parenteral opioids are dosed equivalently; 2) which patient factors affect equianalgesic dose; and 3) which patient factors affect opioid choice.
Design. At a 750-bed tertiary care, teaching hospital in Rochester, NY, patients on the medical and surgical floors and in the emergency department who received one or more doses of parenteral morphine, hydromorphone, or meperidine were identified using computerized pharmacy records. A detailed chart review was performed for each patient, recording a variety of patient variables, which were then correlated separately with opioid dose and choice.
Results. Of the 293 patients treated with boluses of a parenteral opioid, 75% received morphine at a median dose of only 2 mg. Patients prescribed hydromorphone or meperidine received median equianalgesic doses that were 6.7 and 3.4 times higher, respectively. A prescriber’s choice of opioid affected the equianalgesic dose more significantly than any of the patient variables studied, including active home opioid use.
Conclusions. At our institution, parenteral morphine boluses are routinely given at relatively low doses compared with: 1) other opioids; 2) patient-controlled analgesic dosing; 3) usual doses required for analgesia from previous studies; and 4) a historical control in the same hospital. The reasons for this pattern are largely unexplained by patient variables. Inadequate bolus dosing of morphine may be a barrier to appropriate patient analgesia.