OBJECTIVES: This study assessed the daily average consumption (DACON) patterns for oxymorphone extended release tablets and oxycodone hydrochloride controlled release tablets in the treatment of low back pain (LBP) and osteoarthritis (OA). METHODS: Observational, retrospective study of a US commercially insured health plan cohort, which included pharmacy and medical claims for patients with ≥1 diagnosis of LBP and/or OA.  Subjects with OA  and or LBP were identified by ICD-9-CM codes following classifications1,2,3 previously employed. The primary outcome measure for the analysis was DACON which was calculated by dividing the total number of tablets dispensed by the total number of days supply for equianalgesic4 doses of each medication, as defined by an oxymorphone ER:oxycodone HCl CR ratio of 1:2. Patient demographic data were assessed and outcomes were stratified by age, gender, and region comparing users who had claim activity for 2 or more of the two medications for at least 30 days prior to and 90 days after the index date.  The t-test was used to compare mean differences between the two populations for continuous variables.  Multivariate analysis was conducted as a sensitivity analysis in controlling for age, gender, and region heterogeneity. RESULTS:    Data analyzed encompassed approximately 25 million covered lives for the period January 2006 to March 2009.  DACON across all tablet strengths for oxymorphone ER was 2.2 compared to 2.6 for oxycodone CR (p<0.01).  For each formulations maximum strength tablet, oxymorphone ER 40mg DACON was 2.6, compared to 3.7 for oxycodone CR 80 mg (p<0.01).  All statistically significant results for patients with LBP and/or OA had higher DACONs for oxycodone CR than for oxymorphone ER.    CONCLUSIONS: These findings imply that health plan drug policies may need to take into consideration overall usage patterns, patient demographics, and medical diagnoses for long-acting opioids in addition to tablet costs when making formulary decisions.