Background/Purpose: Drug-drug and drug-condition interactions (DDI/DCI) can present a significant challenge to the appropriate prescribing of drugs. The risk of DDI/DCI may be elevated in patients who are treated with polypharmacy or have many comorbid conditions, which is often the case in fibromyalgia (FM) patients. This study quantified the prevalence of potential DDI/DCI in FM patients newly-initiating either pregabalin or duloxetine.

Methods:

Retrospective cohort study using a large U.S. administrative claims database. Studied patients had newly-initiated either pregabalin or duloxetine between 7/1/2008- 10/1/2010 (initiation date=index), were aged ≥18 years at index, had continuous insurance enrollment for ≥12 months pre-index (pre-period) and ≥6 months post-index (post-period), and had ≥1 inpatient or ≥2 outpatient medical claims with a diagnosis of FM (≥1 of which was incurred ≤60 days prior to or on index). Patients were excluded if during the pre- to post-period they resided in a long-term care facility for ≥90 total days or had evidence of epilepsy, post-herpetic neuralgia, transplant surgery, or cancer.

Potential DDI were measured using software (DRUG REAX) which identified instances in which prescriptions that carry a potential for DDI with pregabalin or duloxetine were filled within 180 days before to 30 days after index, with days supply of the potentially interacting drug extending beyond index. Potential DCI were medical conditions listed in the Contraindications and Warnings and Precautions sections of the prescribing information for pregabalin and duloxetine. With the assistance of medical coders, each DCI was assigned an administrative claims-based identification algorithm. The presence of potential DCI was measured during the pre-period. Chi-squared tests compared the prevalence of potential DDI/DCI across the pregabalin and duloxetine initiators.

Results: Study sample comprised 7,751 pregabalin and 7,785 duloxetine initiators; mean age 49 years, 88% female. Among pregabalin initiators, 1.4% had ≥1 potential pregabalin DCI, the most common of which was dizziness (0.9% of patients); none had potential pregabalin DDI. Among duloxetine initiators, 67% had ≥1 potential duloxetine DDI/DCI, largely driven by concomitant drugs carrying a potential for major (45% of patients) or moderate (35% of patients) duloxetine DDI; the most common of which were with tramadol (19% of potential major DDI) and amitriptyline (16% of potential moderate DDI). The prevalence of potential DDI/DCI was significantly different across pregabalin and duloxetine initiators (p<0.001). Of the 107 pregabalin initiators with ≥1 potential pregabalin DCI, 17% had no potential duloxetine DDI/DCI. Of the 5,184 duloxetine initiators with ≥1 potential duloxetine DDI/DCI, 98% had no potential pregabalin DDI/DCI.

Conclusion: In FM patients initiating pregabalin or duloxetine, the prevalence of potential duloxetine DDI/DCI was substantially higher than that of pregabalin. Most duloxetine initiators with a potential duloxetine DDI/DCI had no potential pregabalin DDI/DCI. These findings may have implications to the appropriate prescribing of drugs for the treatment of FM.

---

« Back to 2012 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/prevalence-of-potential-drug-drug-and-drug-condition-interactions-in-fibromyalgia-patients-newly-initiating-pregabalin-or-duloxetine/