Background/Purpose: The combined use of prescription drugs (Rx) with complementary mechanisms of action has been described for treating fibromyalgia (FM). We examined medication adherence and healthcare costs for combination Rx (duloxetine/milnacipran with pregabalin) initiators vs. duloxetine, pregabalin, and milnacipran initiators among privately insured patients with FM.

Methods: Our retrospective cohort study used population-based claims data for the South Carolina Blue Cross Blue Shield State Health Plan (SHP). Patients with FM aged ≥18 years, with Rx initiation during 7/2007 – 6/2010, and SHP enrollment for 12-months pre- and post-index periods were included (combination Rx: N=491, pregabalin: N=1270, duloxetine: N=1460, milnacipran: N=167). Medication initiation was defined as no pill coverage for the Rx in the prior 90 days, and the index-date was defined as the Rx initiation date. Medication adherence measures included high adherence (medication possession ratio ≥80%) and total supply days; healthcare costs comprised direct medical expenditures. Propensity score stratification methods were used to control for selection bias due to differing demographic and clinical characteristics as well as Rx history during the 12-months pre-index. Multivariable regression models that incorporated adjustment for propensity score quintiles were used to compare post-index outcomes, including logistic regression models for high adherence, negative binomial regression models for total supply days, and generalized linear models with a log-link and gamma distributions for expenditures.

Results: Mean age at Rx initiation was 55 years, and 81% were women. Odds ratios for high adherence were significantly increased (p<0.001) among the combination Rx cohort vs. the duloxetine (1.89), milnacipran (3.99), and pregabalin (2.01) cohorts. Rate ratios for total supply days were significantly higher (p<0.0001) for combination Rx vs. duloxetine (1.14), milnacipran (1.34), and pregabalin (1.31). Expenditures for total healthcare and the initiated Rx were significantly higher (p<0.05) for combination Rx vs. duloxetine ($20488 vs. $16202; $2989 vs. $1315; respectively), milnacipran ($21401 vs. $17457; $2877 vs. $717), and pregabalin ($20530 vs. $17516; $2941 vs. $898). However, there were no significant differences observed for direct medical care expenditures (inpatient and/or outpatient services) for combination Rx vs. duloxetine ($11767 vs. $10531, respectively), milnacipran ($11869 vs. $10776), and pregabalin ($11429 vs. $11160), indicating costs neutrality.

Conclusion: Medication adherence was considerably better for combination Rx initiators. Furthermore, expenditure results showed that the use of polypharmacy for combination Rx did not produce a substantial burden to the healthcare system regarding services for direct medical care, indicating that it was safe and well tolerated by patients. Overall, our results suggest important benefits for patients with FM who use combination Rx as part of their multi-modal treatment regimen. Clinical practice guidelines for FM should continue to evolve with the availability of new therapies as well as emerging evidence from population-based naturalistic studies.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/medication-adherence-and-healthcare-costs-among-patients-with-fibromyalgia-combination-medication-versus-duloxetine-pregabalin-and-milnacipran-initiators/