Rivaroxaban

Rivaroxaban is a small-molecule, direct, and selective inhibitor of activated coagulation factor X (factor Xa). By inhibiting factor Xa, rivaroxaban interrupts both the intrinsic and extrinsic pathways of the coagulation cascade at a single critical convergence point, suppressing thrombin generation and subsequent fibrin clot formation. It was the first oral direct factor Xa inhibitor approved for clinical use.

Mechanism of Action

• Direct, competitive inhibition of factor Xa: rivaroxaban binds reversibly to the active site of factor Xa, inhibiting both the free enzyme and factor Xa bound within the prothrombinase complex. The amplification step at which one molecule of FXa generates ~1,000 thrombin molecules is therefore strongly attenuated.
• No antithrombin III requirement: unlike unfractionated heparin and low-molecular-weight heparins, rivaroxaban does not require antithrombin III to exert its anticoagulant effect, allowing oral administration with predictable pharmacodynamics.
• No direct effect on platelets: rivaroxaban does not inhibit platelet aggregation per se, though indirectly reduced thrombin generation diminishes thrombin-mediated platelet activation.
• Coagulation monitoring: PT and aPTT are prolonged in a dose-dependent manner, but neither test is recommended for routine monitoring. Calibrated anti-FXa activity assays can be used when quantification is necessary (perioperatively, in suspected overdose, or in extreme body weights).

Pharmacokinetics

• Absorption: rapid; peak plasma concentration in 2–4 hours. Bioavailability of the 10 mg tablet exceeds 80% under fasted or fed conditions, but the 15 mg and 20 mg tablets must be taken with food to achieve full bioavailability — a clinically important dosing instruction.
• Volume of distribution: approximately 50 L at steady state.
• Protein binding: 92–95%, primarily to plasma albumin.
• Metabolism: approximately two-thirds of an absorbed dose is metabolized hepatically, with CYP3A4, CYP3A5, and CYP2J2 as the main isoenzymes; the remaining fraction is excreted unchanged.
• Half-life: terminal half-life of 5–9 hours in adults; 11–13 hours in elderly patients due to declining renal function.
• Excretion: approximately two-thirds is renal (36% as unchanged drug, 30% as inactive metabolites via active tubular secretion); the remaining third is excreted via faeces.
• Clearance: systemic clearance approximately 10 L/h (low-clearance drug); renal clearance approximately 3–4 L/h.
• Transporters: substrate of P-glycoprotein (P-gp) and BCRP/ABCG2.

• Non-valvular atrial fibrillation (NVAF): prevention of stroke and systemic embolism in adult patients with one or more risk factors.
• Deep vein thrombosis (DVT) and pulmonary embolism (PE): treatment of acute DVT and PE, and prevention of recurrent DVT and PE following initial treatment.
• VTE prophylaxis after elective hip or knee replacement surgery.
• Atherothrombotic event prevention: in combination with low-dose aspirin, reduction of the risk of major cardiovascular events (cardiovascular death, myocardial infarction, stroke) in adults with chronic coronary artery disease or symptomatic peripheral artery disease at high risk of ischaemic events.
• Paediatric VTE: treatment and prevention of recurrence of VTE in children from birth to <18 years; thromboprophylaxis in children aged ≥2 years with congenital heart disease following the Fontan procedure.

• Hypersensitivity to rivaroxaban or any of the excipients.
• Active clinically significant bleeding.
• Lesions or conditions at significant risk of major bleeding (current or recent GI ulceration, malignant neoplasms at high bleeding risk, recent brain or spinal injury, recent brain/spine/eye surgery, recent intracranial haemorrhage, oesophageal varices, arteriovenous malformations, vascular aneurysms, or major intraspinal/intracerebral vascular abnormalities).
• Concomitant treatment with any other anticoagulant (except in defined switching situations or when UFH is used at catheter-maintenance doses).
• Hepatic disease associated with coagulopathy and clinically relevant bleeding risk, including cirrhotic patients with Child-Pugh B and C.
• Pregnancy and breastfeeding.
• Concomitant treatment of acute coronary syndrome with antiplatelet therapy in patients with a prior stroke or transient ischaemic attack.

Common (≥1/100 to <1/10): anaemia, dizziness, headache, haemorrhage (gum, gastrointestinal, urogenital, ocular, skin, post-procedural), epistaxis, haematoma, hypotension, nausea, constipation, diarrhoea, vomiting, abdominal pain, pruritus, rash, pain in extremity, fever, peripheral oedema, transaminase elevations.

Uncommon (≥1/1,000 to <1/100): thrombocytopenia, allergic dermatitis, syncope, tachycardia, dry mouth, hepatic dysfunction, urticaria, renal impairment.

Rare (<1/1,000): jaundice, cholestasis, hepatitis, Stevens-Johnson syndrome / toxic epidermal necrolysis, DRESS syndrome, angioedema, anaphylactic reactions.

Bleeding risk: the dominant safety signal is haemorrhage. Excess post-procedural haemorrhage relative to enoxaparin has been observed in orthopaedic surgery (1.55% vs 1.39%).

• Strong dual CYP3A4 and P-gp inhibitors (azole antifungals — ketoconazole, itraconazole, voriconazole, posaconazole — and HIV protease inhibitors such as ritonavir): substantially increase rivaroxaban exposure; combination is not recommended.
• Strong dual CYP3A4 and P-gp inducers (rifampicin, phenytoin, carbamazepine, phenobarbital, St John’s Wort): substantially decrease rivaroxaban exposure; co-administration should be avoided.
• Other anticoagulants (heparins, LMWH, fondaparinux, dabigatran, apixaban, VKAs): increased bleeding risk; co-administration is contraindicated outside of defined switching scenarios.
• NSAIDs and antiplatelet agents (including aspirin and clopidogrel): additive bleeding risk.
• SSRIs and SNRIs: may modestly increase bleeding risk.
• Grapefruit juice: contains CYP3A4 inhibitors; large quantities may increase exposure.

The 10 mg tablet can be taken with or without food. The 15 mg and 20 mg tablets must be taken with food to ensure full bioavailability. Tablets are swallowed whole; if the patient cannot swallow them whole, they may be crushed and mixed with water or apple puree immediately before administration, followed by food.

Non-valvular Atrial Fibrillation

• Standard dose: 20 mg once daily with food.
• Reduced dose: 15 mg once daily with food in patients with CrCl 15–49 mL/min.

Treatment of DVT/PE

• Initial (first 21 days): 15 mg twice daily with food.
• Maintenance (from day 22): 20 mg once daily with food.
• Extended prevention of recurrence (after at least 6 months of standard treatment): 10 mg once daily; or 20 mg once daily where bleeding risk is judged low and recurrence risk high.

VTE Prophylaxis after Hip or Knee Surgery

• Dose: 10 mg once daily, starting 6–10 hours postoperatively (once haemostasis is established).
• Duration: 5 weeks following hip replacement; 2 weeks following knee replacement.

Chronic Coronary Artery or Peripheral Artery Disease

• Dose: 2.5 mg twice daily in combination with aspirin 75–100 mg once daily.

Renal Impairment

• CrCl ≥50 mL/min: no dose adjustment.
• CrCl 15–49 mL/min: dose adjustments as above; use with caution.
• CrCl <15 mL/min: not recommended.

Hepatic Impairment

• Mild (Child-Pugh A): no dose adjustment.
• Moderate or severe with coagulopathy: contraindicated.

Missed Dose

• Once-daily regimens: take the missed dose immediately and continue normally the next day; do not double up.
• Twice-daily regimens: if the missed dose is recognised on the same day, take it immediately; two 15 mg doses may be taken together on the same day to make up a missed dose during the initial DVT/PE treatment phase.

Bleeding Management

The specific reversal agent andexanet alfa is approved for life-threatening or uncontrolled bleeding on rivaroxaban. Non-specific options include four-factor prothrombin complex concentrate (4F-PCC), activated charcoal (within 2–8 hours of ingestion), and supportive measures. There is no antidote based on protamine sulphate or vitamin K.

Surgical and Invasive Procedures

Rivaroxaban should generally be discontinued at least 24 hours before procedures, with longer intervals (≥48 hours) for procedures carrying a high bleeding risk, in patients with renal impairment, or for spinal/epidural procedures. Restart only once haemostasis is confirmed.

Spinal/Epidural Anaesthesia

Risk of epidural or spinal haematoma is increased; strict timing rules around indwelling catheters and rivaroxaban dosing are required.

Pregnancy and Lactation

• Pregnancy: contraindicated — crosses the placenta; teratogenic potential and fetal bleeding risk.
• Breastfeeding: contraindicated — distributes into breast milk.

Elderly

No specific dose adjustment for age alone, but renal function declines with age; assess CrCl before and during treatment. Increased bleeding risk warrants closer monitoring.

Paediatric Use

Dosing in children is body-weight-based and uses the granules-for-oral-suspension formulation in younger or lighter patients. Paediatric prescribing should follow specialist guidance.

Herbal and Dietary Considerations

Avoid herbs and supplements with anticoagulant or antiplatelet activity (garlic, ginger, bilberry, danshen, ginkgo biloba) and avoid St John’s Wort (potent CYP3A4 inducer).

Effect on Driving

Syncope and dizziness have been reported; patients experiencing these effects should not drive or operate machinery.

This medicinal product does not require any special storage conditions. Keep in the original packaging. Crushed tablets are stable in water and in apple puree for up to 4 hours.

Typically 3 years for the film-coated tablets. Do not use after the expiry date printed on the packaging.

Prescription required (Rx).