Economic impact of potential drug–drug interactions in opioid analgesics

Abstract

Objective:

Patients 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 Design:

This retrospective analysis used paid claims from a large, commercially insured population during January 1, 2004 through December 31, 2008.

Methods:

Propensity matching was used to control for baseline differences in comparisons between 85,043 exposed and 85,043 non-exposed patients.

Results:

Comparisons 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.

Limitations:

The 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).

Conclusion:

Since 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.

Key words::

• Drug interactions
• Economics/econometrics
• Opioid analgesics
• Pharmacoeconomics

Transparency

Declaration of funding

This research was sponsored by Endo Pharmaceuticals.

Declaration of financial/other relationships

Four of the authors are employees of Endo Pharmaceuticals (K.H.S., R.A.P., R.B-J.), and one author is a contract employee (N.R.). One author is a consultant to Endo Pharmaceuticals (R.R.O.).

Acknowledgments

The authors wish to acknowledge an Endo employee and contractors: Steve Cooper for helping develop the research concept; Seongjung Joo, PhD for programming and Chunmay Fu, MS, for quality control.