Continue the home dose of 2.5 mg today (not 5 mg), as the patient's INR is now therapeutic at 2.2 and the recent trend shows they were over-dosed with daily 5 mg in the hospital.
Clinical Reasoning
Your patient's home regimen averages 3.6 mg/day (2.5 mg × 3 days + 5 mg × 4 days = 25 mg/week ÷ 7 = 3.6 mg/day). In the hospital, they received 5 mg daily for 3 consecutive days, which represents a 39% increase in their usual dose. Despite this higher dosing, the INR remained subtherapeutic initially (1.9,1.8) but has now reached the therapeutic range at 2.2.
The key guideline principle here is that for patients with a single out-of-range INR who were previously stable, you should continue the current dose and recheck in 1-2 weeks 1. However, this patient wasn't on their usual dose—they were receiving a higher dose than their established home regimen.
Dosing Decision Algorithm
Step 1: Assess the current INR relative to target
Step 2: Compare hospital dosing to home regimen
- Hospital dose: 5 mg daily = 35 mg/week
- Home dose: 25 mg/week (average 3.6 mg/day)
- The hospital regimen is 40% higher than home
Step 3: Interpret the INR trend
- Days 1-2: Subtherapeutic on 5 mg (INR 1.9,1.8)
- Day 3: Therapeutic on 5 mg (INR 2.2)
- This suggests the patient is responding to the increased dose and will likely continue rising if you maintain 5 mg daily
Step 4: Make the dosing decision
- Return to the home regimen immediately
- Today is the day for 2.5 mg (based on the M/W/F schedule)
- Resume the alternating pattern going forward
Why Not Give 5 mg Today?
If you continue 5 mg daily, you're maintaining a 40% overdose relative to their established maintenance requirement. The INR of 2.2 was achieved on this higher dose, and warfarin has a delayed effect with a half-life of 36-42 hours. Continuing 5 mg daily will likely push the INR above 3.0 within the next few days, increasing bleeding risk unnecessarily 1.
The ACCP guidelines specifically address this scenario: when a patient has a single INR slightly outside or at the edge of therapeutic range (in this case, just entering therapeutic range), continue the established maintenance dose rather than making reactive changes 1. Your patient's established dose is the alternating regimen, not 5 mg daily.
Monitoring Plan
- Recheck INR in 3-5 days (not 1-2 weeks, because you're transitioning back from hospital dosing)
- Once stable on home regimen, return to weekly then monthly monitoring 2, 4, 2
- The goal is to maintain INR 2.0-3.0 for stroke prevention in atrial fibrillation 3
Common Pitfall to Avoid
Do not be tempted to "round up" to 5 mg daily just because it's simpler. The patient was stable on their alternating regimen at home, which suggests this is their true maintenance requirement. Hospital dosing often differs from outpatient regimens due to formulary constraints or simplified protocols, but discharge is the time to return to what actually works for the patient 1.
The evidence shows that time in therapeutic range (TTR) is the most important predictor of outcomes 5, and maintaining a patient's established regimen that previously kept them therapeutic maximizes TTR. Making unnecessary dose changes based on a single therapeutic INR will destabilize their anticoagulation 1.