DOACs-Oral Direct Factor Xa Inhibitors

Question 1

Agents: Rivaroxaban, Apixaban

Mechanism of Action:

Answer 1

• Directly inhibit Factor Xa (independent of antithrombin III).
  
  • Prevent thrombin generation without rebound effect.

Question 2

Pharmacokinetics

Answer 2

APIXABAN:
Bioavailability- high
Half-Life-8-12hrs
Elimination- renal and Hepatic(Dose adjustable in renal impairment)

Rivaroxaban
Bioavailability-High
Half Life- 8–12 hours
Elimination-Primarily renal (avoid in severe renal dysfunction)

Question 3

Indications

Answer 3

Indications (Both Drugs):
* Prevention and treatment of VTE (including DVT and PE).
* Prevention of arterial emboli in nonvalvular atrial fibrillation.

Rivaroxaban dosing: 15 mg BID → 20 mg OD (for VTE/PE treatment).
Lower risk of cerebral hemorrhage than warfarin.

Question 4

Monitoring

Answer 4

Monitoring:
* No reliable or standard test available.
* PT may be elevated, but normal PT does NOT rule out drug presence.
* Chromogenic anti-Factor Xa assay shows promise but is not widely available

Question 5

Reversal agent

Answer 5

Reversal Agent:
* Andexanet alfa (Andexxa):
* FDA-approved for reversal of rivaroxaban and apixaban.
* Mechanism: Decoy receptor that binds Xa inhibitors with high affinity.
* Administered as IV bolus + 2-hour infusion.
* Short-acting → rebound of anticoagulation is common → repeat doses may be required.
* Does NOT reverse dabigatran.