Analgesic tolerance without demonstrable opioid-induced hyperalgesia: a double-blinded, randomized, placebo-controlled trial of sustained-release morphine for treatment of chronic nonradicular low-back pain.
Although often successful in acute settings, long-term use of opioid pain medications may be accompanied by waning levels of analgesic response not readily attributable to advancing underlying disease, necessitating dose escalation to attain pain relief. Analgesic tolerance, and more recently opioid-induced hyperalgesia, have been invoked to explain such declines in opioid effectiveness over time. Because both phenomena result in inadequate analgesia, they are difficult to distinguish in a clinical setting. Patients with otherwise uncomplicated low-back pain were titrated to comfort or dose-limiting side effects in a prospective, randomized, double-blind, placebo-controlled clinical trial using sustained-release morphine or weight-matched placebo capsules for 1 month. A total of 103 patients completed the study, with an average end titration dose of 78 mg morphine/d. After 1 month, the morphine-treated patients developed tolerance to the analgesic effects of remifentanil, but did not develop opioid-induced hyperalgesia. On average, these patients experienced a 42% reduction in analgesic potency. The morphine-treated patients experienced clinically relevant improvements in pain relief, as shown by a 44% reduction in average visual analogue scale pain levels and a 31% improvement in functional ability. The differences in visual analogue scale pain levels (P = .003) and self-reported disability (P = .03) between both treatment groups were statistically significant. After 1 month of oral morphine therapy, patients with chronic low-back pain developed tolerance but not opioid-induced hyperalgesia. Improvements in pain and functional ability were observed.
Department of Anesthesia, Stanford University School of Medicine, Stanford, CA, USA.
Larry F
LF
Chu
Nicole
N
D'Arcy
Caitlin
C
Brady
Abigail Kathleen
AK
Zamora
Chelsea Anne
CA
Young
Julie Eunwoo
JE
Kim
Anna Marie
AM
Clemenson
Martin S
MS
Angst
David J
DJ
Clark
D000293:Adolescent; D000328:Adult; D000368:Aged; D003692:Delayed-Action Preparations / Q000009:adverse effects / Q000627:therapeutic use; D004311:Double-Blind Method; D004361:Drug Tolerance; D005260:Female; D006801:Humans; D006930:Hyperalgesia / Q000139:chemically induced* / Q000175:diagnosis; D017116:Low Back Pain / Q000150:complications / Q000175:diagnosis / Q000188:drug therapy*; D008297:Male; D008875:Middle Aged; D009020:Morphine / Q000009:adverse effects* / Q000627:therapeutic use*; D009293:Opioid-Related Disorders / Q000175:diagnosis / Q000209:etiology*; D010147:Pain Measurement / Q000187:drug effects*; D015990:Placebo Effect; D016896:Treatment Outcome; D055815:Young Adult
D003692:Delayed-Action Preparations; D009020:Morphine