Rivaroxaban vs Dabigatran

## Overview

Rivaroxaban (factor Xa inhibitor) and dabigatran (direct thrombin inhibitor) are both DOACs but with different targets. Dabigatran was the first DOAC approved; it directly inhibits thrombin (factor IIa). Key differences include GI side effects, renal dependence, and specific reversal agents.

## Mechanism of Action

Rivaroxaban: direct Xa inhibitor, blocking prothrombinase complex. Dabigatran: direct thrombin (IIa) inhibitor, preventing fibrinogen-to-fibrin conversion and thrombin-mediated platelet activation. Dabigatran etexilate is a prodrug converted to active dabigatran by intestinal esterases and liver.

## Pharmacokinetics

Dabigatran: bioavailability only ~7% (low but predictable), ~80% renal clearance (highest of all DOACs), half-life 12–17 h, twice daily, capsule must not be crushed (enteric-coated pellets), P-gp substrate. Rivaroxaban: ~80% (with food) bioavailability, ~33% renal clearance, once daily.

## Renal Impairment

Dabigatran's ~80% renal clearance makes it contraindicated in severe renal impairment (CrCl <30 or <15, depending on country/indication). Rivaroxaban requires adjustment but is used cautiously down to CrCl 15 mL/min for some indications. Dabigatran must be avoided in patients with significant CKD.

## Dyspepsia

Dabigatran is associated with significant GI side effects (dyspepsia, GERD-like symptoms) in ~10–35% of patients, a major cause of discontinuation. Rivaroxaban has fewer GI adverse effects.

## Reversal

Dabigatran: idarucizumab (Praxbind) — a monoclonal antibody fragment reversing dabigatran completely within minutes. Rivaroxaban: andexanet alfa (Andexxa).

## Key Takeaways

- Dabigatran: direct thrombin inhibitor, 80% renal clearance, significant dyspepsia, idarucizumab reversal
- Rivaroxaban: Xa inhibitor, lower renal clearance, once daily, andexanet reversal
- Dabigatran contraindicated in severe CKD; rivaroxaban has broader renal use