A 45-year-old woman with hepatic cirrhosis (Child–Pugh Class B) is started on warfarin 5 mg daily for atrial fibrillation. Her baseline INR is 1.2. After 3 days, her INR is 4.8 and she is asymptomatic. What is the most appropriate immediate action?

Question

Accepted Answer

C. Hold warfarin, recheck INR in 24 hours, and resume at a lower dose when INR is in therapeutic range. ## Warfarin Pharmacokinetics in Hepatic Impairment

**Key Point:** Warfarin is metabolized by hepatic cytochrome P450 enzymes (primarily CYP2C9). In cirrhosis, reduced hepatic synthetic function and enzyme activity prolong warfarin half-life, increase bioavailability, and elevate INR disproportionately even at standard doses.

### Warfarin Metabolism & Cirrhosis

| Hepatic Status | Warfarin Clearance | INR Response | Management |
|---|---|---|---|
| Normal | Normal (40–50 h half-life) | Predictable | Standard dosing |
| Mild impairment (Child A) | Mildly reduced | Increased sensitivity | Reduce dose 20–30% |
| Moderate impairment (Child B) | Significantly reduced | Marked sensitivity | Reduce dose 30–50%; close monitoring |
| Severe impairment (Child C) | Severely reduced | Unpredictable, high risk | Avoid if possible; use alternative |

**High-Yield:** This patient has Child–Pugh Class B cirrhosis and achieved supratherapeutic INR (4.8) after just 3 days on standard dosing. This indicates severe warfarin sensitivity due to impaired hepatic metabolism.

### Management Algorithm for Supratherapeutic INR (No Bleeding)

```mermaid
flowchart TD
  A[INR > therapeutic, asymptomatic]:::outcome --> B{INR level?}:::decision
  B -->|4.5-10| C[Hold warfarin]:::action
  C --> D[Recheck INR in 24 h]:::action
  D --> E[Resume at lower dose when INR in range]:::action
  B -->|> 10| F[Hold warfarin + Vitamin K 2.5-5 mg PO]:::action
  F --> G[Recheck INR in 24 h]:::action
```

**Clinical Pearl:** In asymptomatic patients with INR 4.5–10, holding warfarin and rechecking in 24 hours is safer and more physiologic than giving vitamin K (which causes resistance for 7–10 days) or FFP (which is reserved for bleeding or INR >10).

**Warning:** Do NOT give vitamin K 10 mg IV in this scenario — it is excessive, causes warfarin resistance, and makes future anticoagulation difficult. Reserve high-dose vitamin K for INR >10 or active bleeding.

**Tip:** Cirrhotic patients on warfarin require baseline dose reduction (30–50% of normal) and more frequent INR monitoring (every 2–3 days initially, then weekly) to avoid over-anticoagulation.

Answer

A. Administer fresh frozen plasma (FFP) immediately to reverse the effect

Answer

B. Administer vitamin K 10 mg IV and hold warfarin until INR normalizes

Answer

D. Continue warfarin 5 mg daily and recheck INR in 2 days

A 45-year-old woman with hepatic cirrhosis (Child–Pugh Class B) is started on warfarin 5 mg daily for atrial fibrillation. Her baseline INR is 1.2. After 3 days, her INR is 4.8 and she is asymptomatic. What is the most appropriate immediate action?

Explanation

Warfarin Pharmacokinetics in Hepatic Impairment

Warfarin Metabolism & Cirrhosis

Management Algorithm for Supratherapeutic INR (No Bleeding)

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Hepatic Status	Warfarin Clearance	INR Response	Management
Normal	Normal (40–50 h half-life)	Predictable	Standard dosing
Mild impairment (Child A)	Mildly reduced	Increased sensitivity	Reduce dose 20–30%
Moderate impairment (Child B)	Significantly reduced	Marked sensitivity	Reduce dose 30–50%; close monitoring
Severe impairment (Child C)	Severely reduced	Unpredictable, high risk	Avoid if possible; use alternative