A 28-year-old man with a 10-year history of hemophilia A (factor VIII deficiency) presents with acute hemarthrosis of the right knee and severe pain. His baseline factor VIII level is 2%. What is the drug of choice for immediate treatment of this acute bleeding episode?

Explanation

## Acute Hemarthrosis Management in Hemophilia A ### Clinical Context This patient has: - Confirmed hemophilia A (factor VIII deficiency, 2% baseline) - Acute hemarthrosis (joint bleed) — a common, painful complication - Need for rapid factor replacement to prevent joint damage and disability ### Drug of Choice: Recombinant Factor VIII Concentrate **Key Point:** Recombinant factor VIII is the first-line replacement therapy for hemophilia A because it is effective, rapid, and avoids blood-borne pathogen transmission risk. **High-Yield:** Target factor VIII levels for hemarthrosis: - **Acute episode:** 50% (25–40 IU/kg IV bolus) - **Maintenance:** Repeat every 12–24 hours until bleeding stops and pain resolves - **Duration:** Typically 2–3 doses over 24–72 hours **Mnemonic: FACTOR VIII DOSING** — **F**irst dose 25–40 IU/kg, **A**im for 50% level, **C**ontinue q12–24h, **T**arget hemostasis, **O**ptimize pain control, **R**epeat until resolved. ### Mechanism of Action Recombinant factor VIII directly replaces the deficient coagulation factor, restoring the intrinsic pathway and enabling thrombin generation at the site of bleeding. ### Comparative Replacement Options | Product | Source | Onset | Efficacy | Viral Risk | Cost | Use | |---------|--------|-------|----------|-----------|------|-----| | **Recombinant Factor VIII** | Genetic engineering | Rapid (minutes) | Excellent (100% correction) | None | High | **First-line** | | Fresh Frozen Plasma | Donated blood | Slow (30–60 min) | Poor (4% factor VIII) | Present | Low | Obsolete; only if concentrate unavailable | | Prothrombin Complex Concentrate | Donated blood | Rapid | Not indicated (lacks factor VIII) | Present | Moderate | Hemophilia B, not A | | Tranexamic Acid | Synthetic | Rapid | Adjunctive only | None | Low | Adjunct to factor replacement | **Clinical Pearl:** Hemarthrosis is a medical emergency in hemophilia because repeated bleeds lead to hemophilic arthropathy (chronic joint destruction). Early and adequate factor replacement prevents long-term disability. ### Why Not Fresh Frozen Plasma? - Contains only ~1 IU/mL of factor VIII - Requires 10–15 mL/kg to achieve 50% levels (volume overload risk) - Slow onset (30–60 minutes) - Risk of transfusion-transmitted infection - Obsolete in modern hemophilia care ### Why Not Prothrombin Complex Concentrate? - Contains factors II, VII, IX, X (vitamin K–dependent factors) - **Does not contain factor VIII** — useless for hemophilia A - Indicated only for hemophilia B (factor IX deficiency) - Risk of thromboembolism ### Why Not Tranexamic Acid Alone? - Tranexamic acid is a **fibrinolysis inhibitor** (antifibrinolytic) - **Adjunctive agent only** — cannot replace factor VIII - Used alongside factor replacement to stabilize clots - Monotherapy is inadequate for hemarthrosis **Tip:** In exams, always identify the specific deficiency (factor VIII vs. IX vs. V, etc.) before choosing replacement. Hemophilia A = factor VIII; hemophilia B = factor IX. Wrong factor = wrong answer. [cite:Harrison 21e Ch 174]