OBJECTIVE: This study examines the risk factors of narcotic drug use, medical and pharmacy claim costs, and health services use among lower back pain (LBP) patients who use narcotic medications. METHODS: This retrospective study used administrative claims data between September 2002 and March 2004 from 3 employer health plans that collectively contained records of 165,569 employees 18 to 64 years of age. Multivariate regression analyses were performed to examine risk factors and health care services use consequences of narcotic drug use in patients with LBP. RESULTS: The study sample included 13,760 patients with LBP due to mechanical causes. Nearly 60% were female and the average age was 47 years. Almost half of the patients with LBP (45%) used narcotic drugs. Narcotic-using patients with LBP had significantly higher rates of comorbid conditions than patients with LBP not using narcotic drugs; hypertension (23% vs 13%), arthritis (14% vs 4%), depression (10% vs 5%), anxiety (6% vs 3%), and cancer (2% vs 1%) (P<0.001). Patients with LBP with 2 identified psychological comorbid conditions, depression and anxiety, on average used more narcotic medications. Patients with LBP who had surgery were significantly more likely to use narcotic drugs within 1 week of procedure than those patients without surgery (P<0.001). In contrast, patients with LBP who had chiropractic services for LBP were less likely to take narcotic drugs within 7 days after services compared to those without chiropractic services (P<0.001). Furthermore, controlling for health conditions, patients with LBP who took narcotic medications were significantly more likely than patients not taking narcotics to have an emergency room visit within 30 days after the initial narcotic drug prescription dates (P<0.001). Narcotic-using patients with LBP accounted for 62% of health care costs among all patients with LBP. The average monthly health care cost for a narcotic-using LBP patient was $1222, compared to $430 for a LBP patient not using narcotic drugs (P<0.001). CONCLUSIONS: The subjects with LBP who used narcotic medications were more likely to have additional coexisting health conditions and used more health care services than nonusing patients with LBP (P<0.001). Unadjusted health care services costs, including pharmacy claims costs, were significantly higher in patients with LBP using narcotic drugs than in nonusing patients with LBP (P<0.001).