The classification of
morphine as a step III
analgesic, based on pharmacological data, creates a strong bias toward a belief in the efficacy of this
drug. However, double-blind emergency-room trials showed similar levels of
pain relief with intravenous
acetaminophen as with intravenous
morphine in patients with
renal colic,
low back pain or acute limb
pain. In patients with chronic noncancer
low back pain,
morphine and other strong
opioids in dosages of up to 100mg/day were only slightly more effective than their
placebos, no more effective than
acetaminophen, and somewhat less effective than nonsteroidal anti-inflammatory drugs (
NSAIDs). In patients with
osteoarthritis, strong
opioids were not more effective than
NSAIDs and, in some studies, than
placebos. The only randomized controlled trial in patients with
sciatica found no difference with the placebo. Chronic use of strong
opioids can induce
hyperalgesia in some patients. Hyperpathia with increased sensitivity to cold leading the patient to request higher dosages should suggest
opioid-induced
hyperalgesia.
Pain specialists in the US have issued a petition asking that strong
opioids be used in dosages no higher than 100mg/day of
morphine-equivalent, in an effort to decrease the high rate of mortality due to the misuse and abuse of strong
opioids (10,000 deaths/year in the US). Healthcare providers often overestimate the efficacy of step III
analgesics, despite
pain score decreases of only 0.8 to 1.2 points.