Variation in the degree of concentration of prescription opioid utilization using different measures

Studies of opioid prescribing patterns have shown that a small percentage of prescribers are responsible for a large portion of total prescriptions. There is some evidence that prescription opioid use may be similarly concentrated, but patterns may differ by population and choice of opioid utilization measure. The objective of this study is to determine what proportion of prescription opioid utilization was attributable to the top utilizers among Medicaid beneficiaries and how this proportion varies by the measure used.

We analyzed 2008-2009 Medicaid claims data from 14 states and created three claims-based measures of aggregate opioid utilization: total number of annual prescriptions, total annual milligrams morphine equivalent, and total days supply. We tested two versions of the total days supply measure: one assuming consecutive use and the other assuming concurrent use of prescriptions.

The top 20 % of prescription opioid users accounted for 66 % of prescriptions, 82-85 % of days supply depending on assumption, and 90 % of morphine milligram equivalents (MME). The degree to which prescription opioid utilization was concentrated among the top 20 % of users varied minimally across states.

A small percentage of prescription opioid users account for a large share of prescription opioid use. Policy efforts should use metrics pertaining to days supply and total MME, not numbers of prescriptions, to more efficiently target heavy utilization. Policies targeting high-dose prescribing should consider the different ways that overlapping prescriptions may be taken.