Direct Oral Anticoagulants

# Direct oral anticoagulants ## Overview - **Classification**: Factor Xa inhibitors (Apixaban, Rivaroxaban, Edoxaban) or Direct Thrombin Inhibitor (Dabigatran). - **Mechanism**: Directly inhibit specific clotting factors (Factor Xa or Thrombin), preventing clot formation. ## Primary Indications 1. **Stroke Prevention in Non-valvular Atrial Fibrillation (NVAF)** - Reduces risk of embolic stroke and systemic embolism. 2. **Treatment of Deep Vein Thrombosis (DVT) & Pulmonary Embolism (PE)** - Acute treatment and secondary prevention. 3. **Prophylaxis of DVT/PE** - Following orthopedic surgery (e.g., hip/knee replacement). ## Adult Dosing ### Standard Dosing **NVAF Stroke Prevention** - **Apixaban**: - **Dose**: **5 mg** - **Frequency**: Twice daily (BID) - **Route**: Oral - **Special Considerations**: Reduce to **2.5 mg** BID if ≥80 years OR body weight ≤60 kg OR serum creatinine ≥1.5 mg/dL (must have 2 of 3 criteria). - **Rivaroxaban**: - **Dose**: **20 mg** - **Frequency**: Once daily (QD) with evening meal - **Route**: Oral - **Special Considerations**: Reduce to **15 mg** QD with evening meal if CrCl 15-50 mL/min. - **Dabigatran**: - **Dose**: **150 mg** - **Frequency**: Twice daily (BID) - **Route**: Oral - **Special Considerations**: Reduce to **75 mg** BID if CrCl 15-30 mL/min or specific drug interactions. **Treatment of DVT/PE** - **Apixaban**: - **Dose**: **10 mg** BID for 7 days, then **5 mg** BID - **Frequency**: Twice daily (BID), then once daily (QD) - **Route**: Oral - **Duration**: At least 3 months, based on risk. - **Rivaroxaban**: - **Dose**: **15 mg** BID for 21 days, then **20 mg** QD - **Frequency**: Twice daily (BID), then once daily (QD) - **Route**: Oral with food - **Duration**: At least 3 months, based on risk. **Prophylaxis of DVT/PE (e.g., Post-Hip/Knee Surgery)** - **Apixaban**: - **Dose**: **2.5 mg** - **Frequency**: Twice daily (BID) - **Route**: Oral - **Duration**: 12 days (knee) or 35 days (hip). - **Rivaroxaban**: - **Dose**: **10 mg** - **Frequency**: Once daily (QD) - **Route**: Oral - **Duration**: 12 days (knee) or 35 days (hip). ### Dose Adjustments - **Renal Impairment**: - **CrCl <15 mL/min**: Generally **not recommended** for most DOACs; consult specific drug info. - **CrCl 15-50 mL/min**: Dose adjustments needed for Rivaroxaban (NVAF), Dabigatran (NVAF/VTE). Apixaban has criteria. - **Hepatic Impairment**: - **Severe (Child-Pugh C)**: **Contraindicated** for all DOACs due to increased bleeding risk. - **Moderate (Child-Pugh B)**: Use with caution; not recommended for Rivaroxaban/Edoxaban. - **Elderly Patients**: Higher risk of bleeding; dose reductions may be warranted based on renal function or comorbidities. ## Pediatric Dosing *(Note: Pediatric use of DOACs, primarily Rivaroxaban and Dabigatran, is for VTE treatment/prophylaxis and often requires specialist consultation due to complex weight-based dosing and limited data.)* ### Neonates (0-28 days) - **Not generally recommended**: Very limited data; high bleeding risk. - **Special Notes**: Typically not used; consider unfractionated heparin or LMWH. ### Infants (1-12 months) - (Rivaroxaban for VTE treatment/prophylaxis) - **Dose**: Typically **0.2 mg/kg/dose** (oral suspension) for VTE Tx. - **Frequency**: Twice daily (BID) for initial 3 weeks of VTE treatment. - **Maximum**: **2.5 mg/kg/dose** (or as per weight-banded tables). - **Special Notes**: Strict weight-based dosing required. Oral suspension formulation available. ### Children (1-12 years) - (Rivaroxaban for VTE treatment/prophylaxis) - **Dose**: Varies by weight; e.g., **0.2 mg/kg/dose** (suspension) for <30kg, or **15 mg** once daily (tablet) for 30-50kg maintenance. - **Frequency**: Initial VTE Tx often BID, then once daily for maintenance. - **Maximum**: **50 mg/day** (VTE treatment). - **Special Notes**: Oral suspension for <30kg, tablets for >30kg. Consult specific dosing tables. ### Adolescents (13-18 years) - (Rivaroxaban for VTE treatment/prophylaxis) - **Dose**: Follow adult dosing if body weight **>50 kg** (e.g., **20 mg** once daily for VTE maintenance). - **Maximum**: Adult dose. - **Special Notes**: Adult tablets typically used. ## Safety Information ### Contraindications - **Absolute**: Active pathological bleeding. - **Absolute**: Severe hypersensitivity reaction to the drug. - **Absolute**: Hepatic disease associated with coagulopathy and clinically relevant bleeding risk (Child-Pugh B/C for some). - **Absolute**: Presence of artificial heart valves (for dabigatran). - **Absolute**: Pregnancy and Breastfeeding (generally avoid, use LMWH). ### Common Adverse Effects - **Very Common (>10%)**: Bleeding events (epistaxis, GI bleeding). - **Common (1-10%)**: Nausea, dyspepsia, abdominal pain, anemia. - **Serious but Rare**: Major bleeding (intracranial hemorrhage, GI hemorrhage requiring transfusion), allergic reactions. ### Key Drug Interactions - **Strong CYP3A4 and P-glycoprotein (P-gp) Inhibitors (e.g., ketoconazole, ritonavir)**: Significantly increase DOAC levels; **contraindicated** or require dose reduction. - **Strong CYP3A4 and P-gp Inducers (e.g., rifampin, phenytoin, carbamazepine, St. John's wort)**: Significantly decrease DOAC levels; **avoid concomitant use**. - **Other Anticoagulants (e.g., warfarin, heparin, LMWH)**: Greatly increased bleeding risk; **contraindicated** for concurrent use. - **Antiplatelet Agents (e.g., aspirin, clopidogrel)**: Increased bleeding risk; use with caution. ## Monitoring & Follow-up - **Before Treatment**: Baseline CBC (Hgb, Hct, platelets), renal function (CrCl), hepatic function (ALT/AST). - **During Treatment**: - Annually (or more frequently if indicated) check renal and hepatic function. - Monitor for signs/symptoms of bleeding. No routine coagulation monitoring (e.g., INR) is required. - For Dabigatran, specific plasma concentrations can be measured (e.g., using dilute thrombin time, dTT). - For Factor Xa inhibitors, anti-Xa levels can be measured but are not routinely recommended. - **Clinical Signs**: Educate patients to report unusual bruising, prolonged bleeding, bloody/tarry stools, red/dark urine. ## Clinical Pearls - 💡 **Timing Matters**: Take Rivaroxaban with food to maximize absorption. Dabigatran capsules should be swallowed whole. - 💡 **Missed Dose**: Follow specific instructions for each DOAC; generally take as soon as remembered unless close to next dose. Never double dose. - 💡 **Reversal Agents**: Specific reversal agents (idarucizumab for dabigatran; andexanet alfa for Factor Xa inhibitors) are available for life-threatening bleeding. - 💡 **Patient Counseling**: Emphasize importance of adherence, bleeding risk, and informing all healthcare providers about DOAC use. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.