Opioid use for chronic low back pain: A prospective, population-based study among injured workers in Washington state, 2002-2005.
OBJECTIVE
To determine (1) the natural history of prescription opioid use, (2) the predictors of long-term opioid use, and (3) the association between opioid dose and pain and function in a large cohort of workers with recent back injuries.


METHODS
Prospective cohort of workers with back injuries (N=1883) interviewed 18 days (median) and 1 year after claim submission. Detailed pharmacy data were obtained from computerized records of paid bills.


RESULTS
Forty-two percent of workers (781/1843) received an opioid in the year after injury, most (694/781, 89%) at or shortly after the first medical visit for the injury. Of these, most (410/694, 59%) received opioids only within the first quarter after injury, whereas 16% (111/694) received opioids for 4 quarters. Among these long-term users, total morphine equivalent dose (MED) increased significantly (P<0.01) from the first (mean, 2364 mg; standard deviation, 4019 mg) to the fourth (mean, 3824 mg; standard deviation, 5998 mg) quarter. Improvement by at least 30% in pain and function measure scores occurred in only 26% (95% confidence interval 18%-36%) and 16% (95% confidence interval 10%-25%), respectively, of long-term users. Opioid doses increased substantially over time in all but those in whom function improved. After adjustment for baseline pain, function, and injury severity, the strongest predictor of longer term opioid prescription was total MED in the first quarter. Workers receiving at least 40 mg MED per day in the first quarter had 6-fold odds of receiving longer-term opioids.


CONCLUSIONS
For the small group of workers with compensable back injuries who receive opioids longer-term (111/1843, 6%), opioid doses increase substantially and only a minority shows clinically important improvement in pain and function. The amount of prescribed opioid received early after injury strongly predicts long-term use. More research is needed to understand clinical decisions to continue or increase opioid therapy after back injury.
Franklin
Gary M
GM
Departments of Environmental and Occupational Health Sciences, University of Washington, Seattle, USA. meddir@u.washington.edu
Rahman
Enass A
EA
Turner
Judith A
JA
Daniell
William E
WE
Fulton-Kehoe
Deborah
D
D000293:Adolescent; D000328:Adult; D000701:Analgesics, Opioid / Q000009:adverse effects / Q000627:therapeutic use*; D001416:Back Pain / Q000188:drug therapy* / Q000453:epidemiology*; D002908:Chronic Disease; D002986:Clinical Trials as Topic; D018672:Community Health Planning; D016001:Confidence Intervals; D004185:Disability Evaluation; D004305:Dose-Response Relationship, Drug; D011307:Drug Prescriptions / Q000706:statistics & numerical data; D005260:Female; D017048:Health Care Costs / Q000706:statistics & numerical data; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009293:Opioid-Related Disorders / Q000188:drug therapy / Q000209:etiology*; D010147:Pain Measurement / Q000379:methods; D010818:Practice Patterns, Physicians' / Q000706:statistics & numerical data; D012189:Retrospective Studies; D012720:Severity of Illness Index; D013997:Time Factors; D014861:Washington / Q000453:epidemiology; D055815:Young Adult
D000701:Analgesics, Opioid