Anticoagulation & Antiplatelet Therapy

📋 Key Information Summary

📋

Antiplatelet agents (aspirin, P2Y12 inhibitors) target platelet aggregation and are first-line for arterial thrombosis (e.g., ACS, ischaemic stroke).
Anticoagulants (heparins, DOACs, warfarin) target the coagulation cascade and are used for venous thromboembolism (VTE) and atrial fibrillation (AF).
For acute coronary syndrome (ACS), dual antiplatelet therapy (DAPT) with aspirin + a P2Y12 inhibitor is standard; choice of P2Y12 agent depends on clinical presentation and bleeding risk.
For VTE prophylaxis in hospitalised medical patients, use LMWH (e.g., enoxaparin 40 mg SC daily) or fondaparinux 2.5 mg SC daily.
For AF, CHA₂DS₂-VASc score guides anticoagulation need; DOACs (apixaban, rivaroxaban, dabigatran, edoxaban) are preferred over warfarin for most patients.
DOACs require dose adjustment for renal function (eCrCl), weight, age, and interacting medications; always check product information (PI).
UFH infusion requires APTT monitoring; target APTT 1.5–2.5× control for VTE treatment.
LMWH (enoxaparin, dalteparin) is preferred over UFH for most indications; use UFH if eCrCl <30 mL/min or need for rapid on/off effect.
Reversal agents: protamine for heparin, idarucizumab for dabigatran, andexanet alfa for factor Xa inhibitors (apixaban, rivaroxaban), vitamin K for warfarin.
Periprocedural management requires balancing thrombotic vs bleeding risk; use validated protocols (e.g., BRIDGE, PAUSE).
Major bleeding is a medical emergency; stabilise, reverse anticoagulation if possible, and consult haematology.
Consider Aboriginal and Torres Strait Islander patients' higher burden of CVD and VTE, potential barriers to access, and need for culturally safe care.
Medication adherence is critical; use PBS-listed agents where possible and consider dose administration aids for complex regimens.

Introduction & Australian Epidemiology

Anticoagulants and antiplatelet agents are cornerstone therapies for preventing and treating thrombotic disorders. They target distinct pathways: antiplatelet agents inhibit platelet activation and aggregation (primary haemostasis), while anticoagulants interrupt the coagulation cascade (secondary haemostasis). The choice of agent depends on the clinical indication (arterial vs venous thrombosis), patient-specific factors (renal/hepatic function, bleeding risk, age), and practical considerations (route of administration, monitoring, cost).

Cardiovascular disease (CVD) is the leading cause of death in Australia, with ischaemic heart disease accounting for approximately 10% of all deaths in 2022. Atrial fibrillation (AF) affects an estimated 2–4% of the Australian population, increasing stroke risk fivefold. Venous thromboembolism (VTE) has an annual incidence of approximately 0.8–1.6 per 1,000 adults, with significant morbidity and mortality.

This guideline provides an evidence-based, Australian-focused overview of antiplatelet and anticoagulant therapies, emphasising practical prescribing, monitoring, and safety considerations for primary care and specialist practice.

Antiplatelet Agents (Aspirin, P2Y12 Inhibitors)

Antiplatelet agents are primarily used for arterial thrombosis prevention in acute coronary syndromes (ACS), ischaemic stroke, and peripheral arterial disease (PAD).

Aspirin

Aspirin irreversibly inhibits cyclooxygenase-1 (COX-1), reducing thromboxane A2 production. It is the foundation of antiplatelet therapy.

💊

Aspirin

Aspro Clear®, Cardiprin® · Non-selective COX inhibitor

Adult dose (acute) 300 mg PO stat (chewed for ACS), then 100 mg PO daily

Paediatric dose 1–5 mg/kg/day (Kawasaki disease); not for general use in children

Route/Frequency Oral, once daily

Renal adjustment Caution if eGFR <30 mL/min; avoid in severe renal failure

Hepatic adjustment Avoid in severe hepatic impairment

PBS status ✔ PBS General Benefit

P2Y12 Inhibitors

P2Y12 inhibitors block the ADP receptor on platelets, providing more potent platelet inhibition than aspirin alone. Used in dual antiplatelet therapy (DAPT) post-ACS or coronary stenting.

💊

Clopidogrel

Plavix®, Iscover® · Prodrug, CYP2C19 activation

Adult dose 300–600 mg loading, then 75 mg PO daily

Key consideration Variable response due to CYP2C19 polymorphisms

PBS status ✔ PBS General Benefit

💊

Ticagrelor

Brilinta® · Reversible P2Y12 antagonist

Adult dose 180 mg loading, then 90 mg PO BD

Key consideration Faster onset/offset than clopidogrel; dyspnoea common

PBS status ✔ PBS Restricted Benefit (ACS)

💊

Prasugrel

Effient® · Prodrug, rapid activation

Adult dose 60 mg loading, then 10 mg PO daily (5 mg if <60 kg)

Contraindications Prior stroke/TIA, age ≥75, weight <60 kg

PBS status ✔ PBS Restricted Benefit (ACS)

⚠️

Bleeding risk: DAPT increases major bleeding risk 2–3×. Use validated tools (PRECISE-DAPT, HAS-BLED) to assess risk. Proton pump inhibitor (PPI) co-therapy (e.g., pantoprazole) recommended for GI protection.

Heparins (UFH, LMWH) & Fondaparinux

Heparins are parenteral anticoagulants used for acute VTE treatment, prophylaxis, and bridging therapy.

Agent	Mechanism	Key Features	Monitoring
Unfractionated Heparin (UFH)	Potentiates antithrombin III → inactivates IIa, Xa	Short half-life (1–2 h); reversible with protamine; use if eCrCl <30 mL/min or high bleed risk	APTT 6 h post-load, then daily; target 1.5–2.5× control
Enoxaparin (LMWH)	Potentiates antithrombin III → predominantly anti-Xa activity	SC administration; predictable dose-response; lower HIT risk	Anti-Xa level if renal impairment, obesity, pregnancy
Fondaparinux	Synthetic pentasaccharide → selective anti-Xa	Once-daily SC; no HIT risk; renal excretion	Not routinely required

Dosing Examples

💊

Enoxaparin

Clexane®

VTE treatment 1 mg/kg SC BD or 1.5 mg/kg SC daily

VTE prophylaxis 40 mg SC daily (20 mg if eCrCl <30 mL/min)

PBS status ✔ PBS General Benefit

💊

Fondaparinux

Arixtra®

VTE prophylaxis 2.5 mg SC daily

VTE treatment 7.5 mg SC daily (5 mg if <50 kg, 10 mg if >100 kg)

PBS status ✔ PBS Restricted Benefit

🚨

Heparin-Induced Thrombocytopenia (HIT): Monitor platelet count every 2–3 days from day 4. If HIT suspected (platelet drop >50% or thrombosis), stop all heparin immediately and start a non-heparin anticoagulant (e.g., argatroban). Consult haematology.

Direct Oral Anticoagulants (DOACs)

DOACs are first-line for stroke prevention in non-valvular AF and VTE treatment/prevention. They offer predictable pharmacokinetics, fixed dosing, and no routine INR monitoring.

DOAC	Target	Standard AF Dose	Renal Adjustment (AF)	PBS Status
Apixaban	Factor Xa	5 mg PO BD	2.5 mg BD if ≥2 of: age ≥80, weight ≤60 kg, Cr ≥133 µmol/L	PBS General Benefit
Rivaroxaban	Factor Xa	20 mg PO daily with food	15 mg daily if eCrCl 15–49 mL/min; avoid if <15	PBS General Benefit
Dabigatran	Factor IIa (thrombin)	150 mg PO BD	110 mg BD if age ≥80, concomitant verapamil, or eCrCl 30–50 mL/min	PBS General Benefit
Edoxaban	Factor Xa	60 mg PO daily	30 mg daily if eCrCl 15–50 mL/min	PBS Restricted Benefit

ℹ️

Practical tips:

Check renal function (eCrCL using Cockcroft-Gault) at baseline and annually (more often if borderline).
Avoid concomitant strong CYP3A4/P-gp inhibitors (e.g., ketoconazole, ritonavir) or inducers (e.g., rifampicin, carbamazepine).
Missed dose: take if within 6 h (BD drugs) or 12 h (daily drugs) of scheduled time; otherwise skip.

Reversal Agents & Periprocedural Management

Reversal Agents

💉

Idarucizumab

Praxbind® · Dabigatran reversal

Dose 5 g IV (2 × 2.5 g boluses)

Indication Life-threatening bleeding or urgent surgery

PBS status Authority Required

💉

Andexanet alfa

Ondexxya® · Factor Xa inhibitor reversal

Dose Bolus + infusion; dose based on agent, dose, time since last dose

Indication Life-threatening bleeding with apixaban/rivaroxaban

PBS status Authority Required (life-threatening bleed)

💉

Protamine sulfate

Heparin reversal

Dose 1 mg per 100 U UFH (max 50 mg); 1 mg per 1 mg enoxaparin (partial reversal)

Caution Can cause anaphylaxis, hypotension; give slowly IV

PBS status ✔ PBS General Benefit

Periprocedural Management

Use standardised protocols (e.g., PAUSE for DOACs, BRIDGE for warfarin) to balance thrombotic vs bleeding risk.

1

Assess Thrombotic Risk

CHA₂DS₂-VASc (AF), VTE history, mechanical valve. High risk if CHA₂DS₂-VASc ≥5, VTE <3 mo, mechanical mitral valve.

2

Assess Procedural Bleeding Risk

High risk: neuraxial, cardiac, major orthopaedic, urological, bowel resection. Low risk: cataract, minor dental, dermatological.

3

Withhold Anticoagulant

DOACs: hold 24–48 h (depending on drug and renal function). Warfarin: hold 5 days. LMWH bridge only if high thrombotic risk.

4

Restart Post-Procedure

Typically 24–72 h post-surgery, once haemostasis confirmed. Use LMWH bridge if restarting warfarin.

Special Populations

🤰

Pregnancy

Warfarin: Teratogenic; avoid in 1st trimester. Can use in 2nd/3rd trimester with counselling.

LMWH: First-line for VTE treatment/prophylaxis in pregnancy. Dose-adjust by weight; monitor anti-Xa.

DOACs: Contraindicated in pregnancy.

👶

Paediatrics

LMWH: First-line for VTE treatment in children. Dose: 1.5 mg/kg BD (neonates) or 1 mg/kg BD (children).

Warfarin: Used for long-term anticoagulation (e.g., mechanical heart valves). Requires INR monitoring.

DOACs: Limited data; rivaroxaban approved for VTE treatment in children ≥birth (body weight-based dosing).

🩺

Renal Impairment

eCrCl 30–50 mL/min: Dose-adjust DOACs (see table). Enoxaparin: use 1 mg/kg daily for treatment.

eCrCl 15–30 mL/min: Prefer apixaban or warfarin. Enoxaparin: 1 mg/kg daily (monitor anti-Xa).

eCrCl <15 mL/min: Use UFH or warfarin. Avoid DOACs and LMWH.

🫁

Hepatic Impairment

Child-Pugh B/C: Avoid DOACs (increased bleeding risk). Use UFH or warfarin with careful INR monitoring.

Coagulopathy: Correct INR >1.5 before starting anticoagulation if possible.

🦠

Immunocompromised

HIT risk: Higher in post-surgical, oncology patients. Monitor platelets closely.

Drug interactions: Check for interactions with antiretrovirals, azole antifungals, immunosuppressants.

Aboriginal and Torres Strait Islander Health Considerations

Culturally Safe Prescribing and Monitoring

Aboriginal and Torres Strait Islander peoples experience a higher burden of cardiovascular disease and venous thromboembolism compared to non-Indigenous Australians. Anticoagulant and antiplatelet therapy must be tailored to address specific barriers and risks.

Higher CVD & VTE Incidence

Indigenous Australians have 1.7× the rate of acute coronary syndromes and 1.3× the rate of VTE. Ensure aggressive secondary prevention with antiplatelet therapy post-ACS.

Remote Access & Follow-up

Limited pathology services for INR monitoring (warfarin) or renal function checks (DOACs). Consider LMWH for VTE treatment in remote settings if stable and training provided.

Health Literacy & Adherence

Use pictorial medication charts, involve Aboriginal Health Workers, and consider dose administration aids (DAAs) for complex regimens.

Renal Function Considerations

Higher prevalence of CKD; calculate eCrCl before DOAC prescribing. Use lower doses where indicated.

PBS Co-payments & Access

Use PBS-listed agents where possible. Consider Closing the Gap PBS co-payment measure for eligible patients to reduce out-of-pocket costs.

✅

Action: Engage with local Aboriginal Community Controlled Health Organisations (ACCHOs) for shared care plans and culturally appropriate education materials.

📚 References

1. National Heart Foundation of Australia and Cardiac Society of Australia and New Zealand. Australian Clinical Guidelines for the Management of Acute Coronary Syndromes 2023. Heart Lung Circ. 2024;33(1):e1-e91.
2. Australian Commission on Safety and Quality in Health Care (ACSQHC). Blood Management Standard: National Safety and Quality Health Service Standards. 2nd ed. Sydney: ACSQHC; 2021.
3. Tran HA, Gibbs H, Merriman E, et al. New guidelines from the Thrombosis and Haemostasis Society of Australia and New Zealand for the diagnosis and management of venous thromboembolism. Med J Aust. 2019;210(5):227-235.
4. Brieger D, Cullen L, Briffa T, et al. National Heart Foundation of Australia & Cardiac Society of Australia and New Zealand: Australian Clinical Guidance for the Diagnosis and Management of Atrial Fibrillation in Adults. Heart Lung Circ. 2023;32(9):e91-e115.
5. Lip GYH, Banerjee A, Boriani G, et al. Antithrombotic Therapy for Atrial Fibrillation: CHEST Guideline and Expert Panel Report. Chest. 2018;154(5):1121-1201.
6. Australian Institute of Health and Welfare (AIHW). Cardiovascular disease in Aboriginal and Torres Strait Islander people. AIHW, Canberra. 2023.
7. Pollack CV Jr, Reilly PA, van Ryn J, et al. Idarucizumab for Dabigatran Reversal – Full Cohort Analysis. N Engl J Med. 2017;377(5):431-441.
8. Connolly SJ, Crowther M, Eikelboom JW, et al. Full Study Report of Andexanet Alfa for Bleeding Associated with Factor Xa Inhibitors. N Engl J Med. 2019;380(14):1326-1335.
9. Douketis JD, Spyropoulos AC, Duncan J, et al. Perioperative Management of Patients With Atrial Fibrillation Receiving a Direct Oral Anticoagulant. JAMA Intern Med. 2019;179(11):1469-1478.
10. Monagle P, Chan AKC, Goldenberg NA, et al. Antithrombotic Therapy in Neonates and Children: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest. 2012;141(2 Suppl):e737S-e801S.
11. National Aboriginal Community Controlled Health Organisation (NACCHO). Position Statement: Cardiovascular Disease. NACCHO, Canberra. 2022.
12. RHDAustralia (a program of Menzies School of Health Research). RHD Control and Prevention Guidelines. 4th ed. 2022.