• Kent H Summers, R Amy Puenpatom, Niveda Rajan, Rami Ben-Joseph, and Robert Ohsfeldt.
• Department of Health Outcomes and Pharmacoeconomics (HOPE), Endo Pharmaceuticals, 100 Endo Boulevard, Chadds Ford, PA 19317, USA. summers.kent@endo.com
• J Med Econ. 2011 Jan 1;14(4):390-6.

ObjectivePatients managing chronic non-cancer pain with cytochrome P450 (CYP450)-metabolized opioid analgesics who concurrently take another CYP450-metabolized medication experience a drug-drug exposure (DDE), which puts them at risk for a pharmacokinetic drug-drug interaction (PK DDI). This study examined the economic impact of incident DDEs with the potential to cause PK DDIs compared to similar patients without such exposure.Study DesignThis retrospective analysis used paid claims from a large, commercially insured population during January 1, 2004 through December 31, 2008.MethodsPropensity matching was used to control for baseline differences in comparisons between 85,043 exposed and 85,043 non-exposed patients.ResultsComparisons yielded mean total costs 6 months after the DDEs that were significantly higher in subjects with DDE versus matched subjects without DDE [$8165 (SD $11,357) vs. $7498 (SD $11,668), respectively, p<0.01] resulting in a difference of $667. This was driven by medical costs [$5520 (SD $10,505) vs. $5222 (SD $10,689), respectively, p<0.01] a $298 difference, and total prescription costs [$2646 (SD $3262) vs. $2276 (SD $3907), respectively, p<0.01] a $369 difference.LimitationsThe study design demonstrates associations only and cannot establish causal relationships. Further, relevant DDEs were not included if concurrent consumption occurred outside the index period and when CYP450 substances were consumed that are not reflected in pharmacy claims (herbals, over-the-counter medications).ConclusionSince concurrent exposure to DDEs with the potential to cause PK DDIs may be relatively common, policy decisions-makers should consider the use of long-acting opioids that are not metabolized through the CYP450 pathway.

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