Impact of potential pregabalin or duloxetine drug-drug interactions on health care costs and utilization among Medicare members with fibromyalgia

Comparing duloxetine and pregabalin for treatment of pain and depression in women with fibromyalgia: an open-label randomized clinical trial

BACKGROUND

Duloxetine and pregabalin are among the most widely used medications in the treatment of patients with fibromyalgia syndrome (FM).

OBJECTIVES

To add to the very few lines of evidence that exist on the comparative safety and efficacy of these two medications.

METHODS

In this open-label randomized clinical trial, outpatient women, who were diagnosed with FM based on American College of Rheumatology 2010 criteria, and had an age range of 18-65 years old were assigned to either duloxetine 30-60 mg or pregabalin 75-150 mg per day for 4 weeks. Patients were excluded in cases of having used duloxetine, pregabalin, gabapentin, or antidepressants within 12 weeks prior to the study, having had a history of comorbid medical conditions that could provoke chronic pain, or having had comorbid neuropsychiatric disorders, except for major depressive/anxiety disorders. Primary outcomes were between-group differences in mean score changes from baseline to end point for Widespread Pain Index (WPI) and Beck Depression Inventory-II. Secondary outcomes were the same statistical estimates, but for Fibromyalgia Impact Questionnaire-Revised and 12-Item Short Form Survey. Descriptive statistics and independent samples t-test were the main methods of analysis. ( www.irct.ir ; IRCT2016030626935N1).

RESULTS

Among all the scales, only WPI scores improved with a statistically significant difference between the two treatment arms, favoring duloxetine (Mean difference in score change - 2.32, 95% CI, -4.46 to - 0.18; p = 0.034; Cohen's d 0.53 95% CI, 0.04 to 1.02). Drop out rate and cumulative incidence of nausea was significantly higher in the duloxetine arm compared to the pregabalin arm.

CONCLUSION

This study provides further evidence on higher efficacy of duloxetine compared to pregabalin for the treatment of pain in patients with fibromyalgia. Future comprehensive pragmatic clinical trials are warranted.

Cytochrome P450 interactions are common and consequential in Massachusetts hospital discharges

Despite the recognition that drug-drug interactions contribute substantially to preventable health-care costs, the prevalence of such interactions related to the cytochrome P450 system in clinical practice remains poorly characterized. This study drew retrospective hospital discharge cohorts from a large health claims data set and a large health system data set. For every hospital discharge, frequency of co-occurrence of substrates and inducers or inhibitors at cytochrome P450 2D6, 2C19, 3A4 and 1A2 were determined. A total of 124 520 individuals in the state of Massachusetts (health claims cohort) and 77 026 individuals in two large academic medical centers (electronic health record (EHR) cohort) were examined. In the claims cohort, 35 157 (28.2%) exhibited at least one CYP450 drug-drug interaction at hospital discharge, whereas in the EHR cohort, 36 750 (47.7%) had at least one interaction. The most commonly affected CYP450 systems were 2C19 and 2D6, with putative interactions observed in at least 10% of individuals at discharge in each cohort. Odds of hospital readmission within 90 days among those discharged with at least one interaction were 10-16% greater, with mean health-care cost $574/month greater over the subsequent year, after adjusting for age, sex, insurance type, total number of medications prescribed, Charlson comorbidity score and presence or absence of a psychiatric diagnosis. These two distinct clinical data types show that CYP450 drug-drug interactions are prevalent and associated with greater probability of early hospital readmission and greater health-care cost, despite the widespread availability and application of drug-drug interaction checking software.