ACCEL | With the advent of novel oral anticoagulants (NOACs) that do not require the regular blood testing or dietary restrictions associated with warfarin, how do patients feel about switching? In a survey of 155 patients attending the Warfarin Clinic of the Rush University Medical Center, 80% of patients reported satisfaction with warfarin, but 58% were willing to switch anticoagulants.¹ Women were significantly less willing to switch from warfarin than men (p = 0.003) and respondents older than 70 years were significantly more willing to switch anticoagulants than their younger counterparts (p = 0.017).

Another study of 269 patients attending the Georgia Regents Health System pharmacy-based anticoagulation clinic also found high satisfaction with warfarin treatment.² Patient satisfaction was rated on a scale of 1-5; with warfarin, the score was 4.7±0.78, but a vast majority of the patients were willing to switch to an agent that:

• requires less frequent follow-up visits (3.9±1.35);
• lacks interaction with food and/or beverages (4.1±1.25);
• is as efficacious as warfarin (3.7±1.38).

Among patients who were less willing to switch, one important issue was that out-of-pocket costs (>$50) would be a major barrier to changing to a new medication.

Appropriate Candidates
William L. Baker, Jr., PharmD, offers some ideas on appropriate candidates for switching to a NOAC: good prescription coverage, normal renal function, and no history of gastrointestinal bleeding, for instance. For patients on warfarin, has there been INR (international normalized ratio) instability requiring frequent dose changes?

Looking at it from a different angle, the quality of anticoagulation control (as reflected by the time in therapeutic range [TTR] for INR) is an important determinant of thromboembolism and bleeding. AFFIRM trial investigators analyzed the clinical factors associated with TTR and developed the SAMe-TT2R2 score, an assessment tool to predict the likelihood of poor INR control in atrial fibrillation (AF) patients on warfarin (TABLE).³

Based on their analysis, a patient with a score of 0-1 should do well on warfarin, while a score of ≥2 is a patient more likely to require additional intervention to achieve acceptable anticoagulation control.

Switching NOACs
The manufacturers offer guidance relating to switching from warfarin to NOACs:

• to apixaban: warfarin should be discontinued and apixaban started when the INR is <2.0
• to dabigatran: warfarin should be discontinued and dabigatran started when the INR is <2.0
• to rivaroxaban: warfarin should be discontinued and rivaroxaban started when the INR is <3.0

As for bleeding when making a switch, Dr. Baker said no bleeding hazard was seen with prior warfarin use in ARISTOTLE (apixaban) or RE-LY2 (dabigatran)—and both started the NOAC when INR was <2.0.

Recent data from ROCKET AF (rivaroxaban) did show higher bleeding rates versus warfarin (3.9% vs. 3.3%) in warfarin-experienced patients.⁴ Higher clinically relevant bleeding was seen with the NOAC versus warfarin during the first 7 days (1.54% vs. 0.20%) and, as recommended, the NOAC was initiated when INR was <3.0. However, after 30 days, rivaroxaban was associated with less bleeding than warfarin in warfarin-naive patients (HR = 0.84 [95% CI 0.74 to 0.95]) and similar bleeding in warfarin-experienced patients (HR = 1.06 [95% CI 0.96 to 1.17]; interaction p = 0.003).

With longer experience with these NOACs in Europe, the European Heart Rhythm Association does make slightly different recommendations than those in the United States.⁵ Again, looking at switching from a vitamin K antagonist to a NOAC, the group suggests:

• the NOAC can be immediately initiated once the INR is <2.0
• if the INR is 2.0 to 2.5, the NOAC can be started immediately or (preferably) the next day
• if the INR is >2.5, use agent pharmacokinetics to estimate the time for the next INR

As for moving from parenteral anticoagulation to a NOAC, the European recommendation is:

• for unfractionated heparin (UFH), start the NOAC once the UHF is discontinued
• for low-molecular weight heparin (LMWH), start the NOAC when the next dose of LMWH would have been due

References

1. Attaya S, Bornstein T, Ronquillo N, et al. Am J Ther. 2012;19:432-5.
2. Elewa HF, Deremer CE, Keller K, et al. J Thromb Thrombolysis. 2013;38:115-20.
3. Apostolakis S, Sullivan RM, Olshansky B, Lip GY. Chest. 2013;144:1555-63.
4. Mahaffey KW, Wojdyla D, Hankey GJ, et al. Ann Intern Med. 2013;158:861-8.
5. Heidbuchel H, Verhamme P, Alings M, et al. Europace. 2013;15:625-51.

To listen to an interview with William L. Baker, Jr., PharmD, about anticoagulant switching, visit youtube.cswnews.org. The interview was conducted by Christopher M. Kramer, MD.

Keywords: CardioSource WorldNews Interventions

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