Split-tablet equals alternating-day warfarin dosing

Split-tablet and alternating-day dosing regimens of warfarin yield comparable outcomes such as the international normalized ratio (INR), compliance, time in therapeutic range (TTR), and complications, a recent study has found.

Researchers enrolled 66 patients who were randomly assigned to receive split-tablet (n=32; mean age 58.0 years, 43.8 percent men) or alternate-day (n=34; mean age 59.1 years, 50.0 percent men) warfarin dosing regimens. The primary outcome of interest was TTR of 2.0–3.0 percent, while secondary endpoints included compliance, INR, total dosage, and anticoagulant-related events.

The overall TTR in the intention-to-treat population was 73.9 percent. Such outcome was slightly higher in patients who received alternate-day vs split-tablet warfarin dosing (74.9 percent vs 72.8 percent). The resulting difference of –2.1 percentage points was not statistically significant (95 percent confidence interval, –13.7 to 9.6; p=0.72).

Both dosing regimens likewise proved comparable in terms of secondary endpoints. For example, mean INR was 2.45 in the split-tablet arm and 2.53 in the alternate-day group (p=0.39). Similarly, 3.1 percent and 18.8 percent of participants receiving the corresponding warfarin regimens needed dose adjustments for inadequate INR (p=0.10).

Minor bleeding events likewise occurred at comparable rates between split-tablet and alternate-day regimens (18.8 percent vs 31.2 percent, respectively; p=0.25). The same was true for the incidence of drug or food interactions (18.8 percent vs 21.9 percent, respectively; p=0.76). No cases of major bleeding or thromboembolic events arose.

Drug compliance was likewise not significantly affected by dosing regimen (p=1.00).