Warfarin Management After Missed Doses and Subtherapeutic INRs

Maintenance Dose Strategy

The American College of Chest Physicians (ACCP) recommends that patients with previously stable therapeutic INRs who present with a single INR ≥ 0.5 below the therapeutic range should continue their current maintenance dose rather than adjust it. [1]
A randomized controlled trial found no significant advantage of a one‑time dose increase compared with maintaining the same dose for out‑of‑range INRs (1.5–4.4) in achieving a therapeutic INR at 2 weeks (44 % vs 40 %; OR 1.17, 95 % CI 0.59–2.30). [1] – moderate‑quality evidence.
A dosing model based on 3,961 patients showed that warfarin doses do not need adjustment for INRs between 1.7 and 3.3. [1] – observational evidence.

The ACCP advises that heparin bridging is not routinely recommended for a single subtherapeutic INR. [1]
A retrospective cohort of 2,597 patients with subtherapeutic INRs after two therapeutic measurements demonstrated no significant difference in thromboembolic events compared with patients who remained in the therapeutic range. [1] – retrospective evidence.
In a series of 294 patients with mechanical heart valves and subtherapeutic INRs, the incidence of thromboembolic events was 0.3 % (95 % CI 0 %–1.9 %) when no bridging therapy was used. [1] – observational evidence.

The ACCP recommends rechecking the INR within 1–2 weeks after missed doses; a 3–7 day interval is considered reasonable. [1]
The American Society of Hematology (ASH) suggests that recall intervals of 2–4 weeks are appropriate after dose adjustments for moderately out‑of‑range INRs in patients with generally stable control, but more frequent monitoring (within a few days) is warranted after a temporary interruption of warfarin. [6] – guideline recommendation.
Consensus guidance advises scheduling an INR recheck in 3–7 days to confirm return to the therapeutic range following missed doses. [6]

All facts are derived from cited sources and reflect guideline recommendations, randomized trial data, or large observational studies.