A 62-year-old woman with unstable angina (chest pain at rest, troponin negative, ST-segment depression on ECG) is admitted to the coronary care unit. She has no contraindications to anticoagulation. Which of the following is the drug of choice for anticoagulation in this patient?

Explanation

## Anticoagulation in Unstable Angina / NSTEMI **Key Point:** Low-molecular-weight heparin (LMWH), particularly enoxaparin, is the **preferred anticoagulant** in unstable angina and NSTEMI due to superior efficacy, predictable pharmacokinetics, and ease of administration. ### Anticoagulant Comparison in ACS | Agent | Route | Monitoring | Advantages | Disadvantages | | --- | --- | --- | --- | --- | | **Enoxaparin (LMWH)** | SC/IV | Minimal (weight-based) | Predictable PK, superior outcomes (ESSENCE trial), no monitoring | Renal clearance (caution in CKD) | | **UFH** | IV infusion | aPTT monitoring | Shorter half-life, reversible, PCI-friendly | Unpredictable PK, HIT risk, requires monitoring | | **Fondaparinux** | SC | Minimal | Once-daily dosing, selective Xa inhibition | **Contraindicated in acute coronary syndrome** (increased stent thrombosis risk) | | **Warfarin** | Oral | INR monitoring | Long-term anticoagulation | Slow onset (days), not for acute phase, requires bridging | **High-Yield:** Enoxaparin is the **drug of choice** because: 1. **Superior efficacy** — ESSENCE and TIMI 11B trials showed LMWH reduces recurrent ACS vs UFH 2. **Predictable pharmacokinetics** — weight-based dosing, no aPTT monitoring needed 3. **Convenient** — SC or IV administration, twice-daily dosing 4. **Rapid onset** — therapeutic levels within 30 min **Clinical Pearl:** UFH is preferred **only** in specific scenarios: - Severe renal impairment (CrCl < 30 mL/min) — enoxaparin accumulates - Planned urgent PCI within hours — shorter half-life allows rapid reversal - High bleeding risk requiring rapid reversal with protamine **Warning:** Fondaparinux is **contraindicated in acute coronary syndrome** — the OASIS-6 trial showed increased stent thrombosis when used in ACS. It is reserved for chronic anticoagulation in stable CAD or VTE. ### Treatment Algorithm ```mermaid flowchart TD A[Unstable Angina/NSTEMI]:::outcome --> B[Dual Antiplatelet + Anticoagulation]:::action B --> C{Renal Function?}:::decision C -->|CrCl ≥ 30| D[Enoxaparin 1 mg/kg SC BD]:::action C -->|CrCl < 30| E[UFH IV infusion]:::action D --> F[Preferred first-line]:::outcome E --> G[Alternative in renal disease]:::outcome B --> H{Urgent PCI?}:::decision H -->|Yes, within hours| I[UFH preferred]:::action H -->|No| J[LMWH acceptable]:::action ``` [cite:Harrison 21e Ch 297]