# AI tells a patient on warfarin that INR monitoring every 2 weeks is sufficient after a dose change, ignoring need for more frequent checks

- **ID:** `medical/warfarin-inr-monitoring-frequency`
- **Domain:** medical
- **Category:** runtime_error
- **Error Code:** `WARFARIN-INR-FREQ-ERR`
- **Verification:** ai_generated
- **Fix Rate:** 88%

## Root Cause

After warfarin dose adjustment, INR should be rechecked within 3-7 days due to the drug's narrow therapeutic index and variable response; waiting 2 weeks risks subtherapeutic or supratherapeutic INR, increasing thromboembolic or bleeding risk.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| Warfarin Sodium 5mg Tablets USP | active | — | — |
| Coumadin 5mg | active | — | — |
| Jantoven 5mg | active | — | — |
| INRatio PT/INR Monitor | active | — | — |

## Workarounds

1. **After any warfarin dose adjustment (increase or decrease), schedule INR check within 3-7 days. Use a standardized algorithm (e.g., the '5-7 day rule'). If INR is within target range (e.g., 2.0-3.0 for most indications), extend to every 2 weeks, then monthly after two consecutive stable values.** (90% success)
   ```
   After any warfarin dose adjustment (increase or decrease), schedule INR check within 3-7 days. Use a standardized algorithm (e.g., the '5-7 day rule'). If INR is within target range (e.g., 2.0-3.0 for most indications), extend to every 2 weeks, then monthly after two consecutive stable values.
   ```
2. **For patients on long-term stable warfarin, use a point-of-care INR device (e.g., CoaguChek) for weekly self-monitoring with remote dose adjustment via anticoagulation clinic. This reduces clinic visits while maintaining safety.** (85% success)
   ```
   For patients on long-term stable warfarin, use a point-of-care INR device (e.g., CoaguChek) for weekly self-monitoring with remote dose adjustment via anticoagulation clinic. This reduces clinic visits while maintaining safety.
   ```

## Dead Ends

- **** — The patient may have been subtherapeutic for 10+ days, but doubling dose could cause overshoot to >5.0 and major bleeding. Need to check at 3-7 days after adjustment. (80% fail)
- **** — Even stable patients can have INR fluctuations due to diet, illness, or other medications. Monthly monitoring is standard for stable patients, but more frequent checks are needed after any dose change. (70% fail)