Abstract P241: Treatment Persistence Among Atrial Fibrillation/Flutter Patients on Combination Warfarin and Antiarrhythmic Drug Therapy in the Real-World Setting

Abstract

Background: Antiarrhythmic drugs and warfarin (W) are often co-administered for atrial fibrillation/flutter (AF/AFL). Amiodarone (A) potentiates the anticoagulant effect of W, necessitating frequent INR monitoring and dose adjustment. We compared real-world treatment persistence in AF/AFL patients (pts) receiving W + A or W + another Class I/III antiarrhythmic drug (Other AAD). Methods: This retrospective cohort study identified AF/AFL pts ≥18 yrs with concurrent pharmacy claims (≥ 60 days' supply over first 90 days) for W and A or Other AAD from the Ingenix IMPACT database (1997-2009). Eligible pts had ≥1 claims with an AF/AFL diagnosis ≤6 months before starting concomitant W + A or W + Other AAD (‘index date’) and continuous pre- (≥6 months) and post-index (≥12 months) enrollment. Drug discontinuation (≥ 60-day gap between consecutive prescriptions) was recorded over 1 year from the index date. Pts were censored at first discontinuation of either drug (last day with supply before 60-day gap) or after 1 year. Times to drug discontinuation (either drug and W and AAD separately) were compared using Cox proportional hazards models. Results: 4,238 pts (mean age 66.5 yrs; 70% male; mean Charlson Comorbidity Index [CCI] 1.76) received W + A and 6,332 pts (mean age 61.9 yrs; 65% male; mean CCI 0.89) received W + Other AAD. Over 1-year post-index, the W + A cohort had higher rates of discontinuation of warfarin (51.7% vs 43.4%), AAD (53.1% vs 32.9%) or either drug (72.7% vs 58.3%) than the W + Other AAD cohort (all P <0.0001) (Table). After adjusting for demographic/clinical differences, the W + A cohort was at higher risk of discontinuing warfarin (hazard ratio [HR] 1.33, 95% CI 1.25−1.42), AAD (HR 1.92, 95% CI 1.80−2.06) or either drug (HR 1.54, 95% CI 1.46−1.62) than the W + Other AAD cohort (all P <0.0001). Treatment discontinuation rate - either drug 90 days 180 days 360 days Warfarin + Amiodarone 19.1% 48.5% 72.7% Warfarin + Other AAD 14.0% 36.6% 58.3% Conclusion: In real-world practice, AF/AFL pts are less persistent with W + A than with W + Other AAD combination therapy. The reasons for this difference remain to be established.