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# Direct Oral Anticoagulants (DOACs)
## Overview
DOACs are target-specific oral anticoagulants, including direct thrombin inhibitors (Dabigatran) and Factor Xa inhibitors (Apixaban, Rivaroxaban, Edoxaban). They offer predictable pharmacokinetics with no routine coagulation monitoring required.
## Primary Indications
* Treatment and prophylaxis of venous thromboembolism (VTE/PE).
* Stroke prevention in non-valvular atrial fibrillation (NVAF).
* Prophylaxis following elective hip or knee replacement (Rivaroxaban, Apixaban, Dabigatran).
## Adult Dosing
* **Apixaban (NVAF):** 5 mg PO BID. Reduce to 2.5 mg BID if ≥2 of the following: Age ≥80, weight ≤60 kg, or Scr ≥1.5 mg/dL.
* **Rivaroxaban (NVAF):** 20 mg PO daily with evening meal.
* **Dabigatran (NVAF):** 150 mg PO BID. (110 mg BID used in some regions/high bleed risk).
* **Edoxaban (NVAF):** 60 mg PO daily. Avoid if CrCl >95 mL/min (paradoxical reduced efficacy).
## Pediatric Dosing
* Dosing varies significantly by age and weight. Pediatric protocols (e.g., CHEST guidelines) require weight-based nomograms.
* **Rivaroxaban/Dabigatran:** Approved for pediatric VTE treatment in some jurisdictions (e.g., FDA-approved for ages <18 years). Doses are strictly body-surface area or weight-based. **Consult specific institutional protocols and official labeling for pediatric use as dosing is highly individualized.**
## Dose Adjustments
* **Renal Impairment:** Mandatory for all DOACs.
* **Apixaban:** CrCl <15 mL/min: No established dosing (use with caution).
* **Rivaroxaban:** Avoid if CrCl <15 mL/min.
* **Dabigatran:** Contraindicated if CrCl <30 mL/min in most NVAF guidelines.
* **Edoxaban:** Contraindicated if CrCl >95 mL/min; reduce dose if CrCl 15–50 mL/min.
## Contraindications
* Active pathological bleeding.
* Mechanical heart valves (Dabigatran is specifically contraindicated).
* Moderate-to-severe hepatic impairment (Child-Pugh B or C).
* Known hypersensitivity.
## Adverse Effects
* Major and minor bleeding (GI bleeding is more frequent with Dabigatran and Rivaroxaban compared to Warfarin).
* Dyspepsia (Dabigatran specifically).
* Anemia.
## Key Drug Interactions
* **P-gp and Strong CYP3A4 inhibitors/inducers:** Co-administration with strong inhibitors (e.g., ketoconazole, clarithromycin) may increase levels; strong inducers (e.g., rifampin, carbamazepine, St. John’s wort) decrease efficacy.
* **Antiplatelets/NSAIDs:** Significantly increase the risk of major hemorrhage.
## Monitoring
* Baseline: CBC, Scr, LFTs, and coagulation profile (though DOACs do not require routine INR monitoring).
* Periodic: Renal function (serum creatinine) at least annually (more frequent in elderly or those with CrCl <60 mL/min).
* No standardized assay for routine monitoring; anti-FXa levels may be used in select centers for emergency situations.
## Clinical Pearls
* **Reversal:** Idarucizumab is the specific reversal agent for Dabigatran. Andexanet alfa is used to reverse Apixaban and Rivaroxaban in life-threatening bleeding.
* **Transitioning:** DOACs are preferred over Warfarin for most NVAF patients due to reduced intracranial hemorrhage risk.
* **Compliance:** Due to short half-lives, missed doses lead to rapid loss of anticoagulation. Ensure patient adherence is high.
***
*Disclaimer: This information is for educational purposes only. Direct oral anticoagulant dosing is complex and dependent on renal function, indication, and regional regulatory guidelines. Always verify current prescribing information, institutional protocols, and patient-specific factors before prescribing or administering these medications.*
