Injectable anticoagulant indicated for prophylaxis of deep vein thrombosis in patients undergoing major orthopedic surgery (hip fracture, hip and knee replacement) and at-risk abdominal surgery, and for treatment of acute DVT and acute pulmonary embolism.
Also known as: Arixtra, fondaparinux sodium
DailyMed approved label (Fondaparinux Sodium Injection, Zydus; setID dffbf7c9-495e-4a33-ac76-57b52f014fc2).
DailyMed approved label (Fondaparinux Sodium Injection, Zydus; setID dffbf7c9-495e-4a33-ac76-57b52f014fc2).
Fondaparinux + warfarin: increased bleeding risk — monitor closely if the combination is needed.
The FDA fondaparinux label documents the increased bleeding risk when combined with drugs affecting haemostasis (including warfarin, NSAIDs and antiplatelets). Fondaparinux is a selective factor Xa inhibitor and warfarin antagonises the synthesis of vitamin K-dependent factors: the mechanisms are complementary, so the risk of major bleeding (including intracranial and retroperitoneal) is additive. Overlap is common in the therapeutic bridge to warfarin (e.g., DVT/PE), but requires active vigilance: monitor for signs of bleeding, haemoglobin and, during prolonged overlap, INR until the therapeutic range is reached. Higher-risk patients are the elderly, low body weight and renal impairment, which accumulate fondaparinux. There is no absolute contraindication — the combination is standardised in protocols — but dual anticoagulation should be limited to the bridge period and monitored.
Fondaparinux + warfarin: additive bleeding risk — monitor closely when anticoagulant overlap is necessary.
The FDA fondaparinux label documents: "Agents that may enhance the risk of hemorrhage should be discontinued prior to initiation of therapy with fondaparinux sodium unless these agents are essential. If co-administration is necessary, monitor patients closely for hemorrhage" (7). Warfarin, an oral anticoagulant, adds bleeding risk with fondaparinux.
Monitor for bleeding (clinical and laboratory — haemoglobin, platelets) and INR during overlap.
Active bleeding, falling haemoglobin or spontaneous bruising during the combination.
Discontinue agents that increase bleeding risk before starting fondaparinux unless essential; if the combination is necessary, monitor closely.
DailyMed/FDA (NIH/NLM) — approved Fondaparinux label (section 7 Drug Interactions): https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=41a37a19-1bf8-4ba0-a12d-dbb6cc8c295c ; approved Warfarin label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=5c29b4b1-e7e0-4b28-8ea9-e2b103d3d85e
Fondaparinux + aspirin: increased bleeding risk — monitor closely if the combination is needed.
The FDA fondaparinux label warns that concomitant use with drugs affecting haemostasis — including NSAIDs, platelet aggregation inhibitors and other anticoagulants — increases the risk of bleeding. Aspirin irreversibly inhibits platelet COX-1 and impairs aggregation, while fondaparinux inhibits factor Xa: the combination adds independent haemostasis mechanisms and raises the risk of gastrointestinal and other-site bleeding. In patients with a dual indication (e.g., acute coronary syndrome + prophylaxis/thromboembolism), the combination is sometimes unavoidable and is used for a limited duration. The practical guidance is to monitor for signs of bleeding (melena, haematuria, haemoglobin drop) and consider gastric protection in at-risk patients, without stopping the antiplatelet without cardiovascular assessment.
Fondaparinux + aspirin: additive bleeding risk (NSAIDs/antiplatelets) — limit the combination and monitor for bleeding.
The FDA fondaparinux label documents that platelet inhibitors (acetylsalicylic acid) do not affect fondaparinux pharmacokinetics, but "Agents that may enhance the risk of hemorrhage should be discontinued prior to initiation of therapy with fondaparinux sodium unless these agents are essential" (7). Aspirin, a platelet inhibitor, adds bleeding risk.
Monitor for bleeding (clinical and laboratory) during the combination.
Active bleeding or falling haemoglobin during the combination.
Discontinue aspirin before starting fondaparinux unless essential; if the combination is necessary, monitor closely.
DailyMed/FDA (NIH/NLM) — approved Fondaparinux label (section 7 Drug Interactions): https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=41a37a19-1bf8-4ba0-a12d-dbb6cc8c295c ; approved Aspirin label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=4ac7de91-7d38-4c1d-9c49-b08307b4ecc1
Fondaparinux + diclofenac: increased bleeding risk (NSAID) — monitor closely.
The FDA fondaparinux label explicitly includes NSAIDs among the drugs that increase bleeding risk when used concomitantly. Diclofenac inhibits COX-1 and COX-2, reduces platelet aggregation and damages the gastric mucosa, while fondaparinux inhibits factor Xa: the haemostasis mechanisms affected are complementary and the risk of gastrointestinal and other-site bleeding is additive. In anticoagulated patients requiring analgesia, alternatives with less impact on haemostasis (e.g., adequate-dose paracetamol) should be preferred whenever possible. If the NSAID is unavoidable, use the lowest dose and shortest duration, with gastric protection in at-risk patients and monitoring for signs of bleeding.
Fondaparinux + diclofenac: additive bleeding risk (NSAID) — avoid or limit the combination.
The FDA fondaparinux label documents that NSAIDs (e.g., piroxicam in studies) do not affect fondaparinux pharmacokinetics, but "Agents that may enhance the risk of hemorrhage should be discontinued prior to initiation of therapy with fondaparinux sodium unless these agents are essential" (7). NSAIDs such as diclofenac increase bleeding risk through platelet inhibition and gastrointestinal irritation.
Monitor for bleeding and gastrointestinal symptoms during the combination.
Active bleeding, melaena or abdominal pain with the combination.
Discontinue NSAIDs before starting fondaparinux unless essential; if the combination is necessary, monitor closely.
DailyMed/FDA (NIH/NLM) — approved Fondaparinux label (section 7 Drug Interactions): https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=41a37a19-1bf8-4ba0-a12d-dbb6cc8c295c ; approved Diclofenac label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=97bd5a1e-5c20-4a1b-9cd1-ccf55b1bf7ce
Fondaparinux is given subcutaneously; food does not affect its pharmacokinetics.
May be administered regardless of meals.
DailyMed approved label (Fondaparinux Sodium Injection, Zydus; setID dffbf7c9-495e-4a33-ac76-57b52f014fc2).
No relevant pharmacokinetic interaction; excessive alcohol can increase the risk of falls/bleeding in anticoagulated patients.
Moderate alcohol intake during treatment.
DailyMed approved label (Fondaparinux Sodium Injection, Zydus; setID dffbf7c9-495e-4a33-ac76-57b52f014fc2).
Fondaparinux is renally eliminated and is contraindicated at CrCl < 30 ml/min.
Do not use at CrCl < 30 ml/min; assess renal function before starting.
EMC-UK (MHRA) — approved Fondaparinux SmPC: https://www.medicines.org.uk/emc/product/3340/smpc
Data on fondaparinux in pregnancy are limited; use only if the benefit outweighs the risk.
Avoid in pregnancy unless strictly necessary.
Excretion into breast milk is unknown; use with caution.
In women of childbearing age, rule out pregnancy before starting.
EMC-UK (MHRA) — approved Fondaparinux SmPC: https://www.medicines.org.uk/emc/product/3340/smpc ; Prontuário Terapêutico do INFARMED (11th ed., 2012) — Annex 2, Drugs and Breastfeeding: Avoid; present in milk in animal studies.
Clinical and educational support tool. The information does not replace a medical prescription or the opinion of a qualified healthcare professional.
Antithrombotic activity results from antithrombin III-mediated selective inhibition of factor Xa: by selectively binding ATIII, it potentiates (~300-fold) the neutralization of factor Xa, interrupting the coagulation cascade and inhibiting thrombin formation. It does not inactivate thrombin nor affect platelet function.
Synthetic pentasaccharide that selectively binds antithrombin III (ATIII), potentiating factor Xa neutralization; pharmacodynamics are monitored by anti-Xa activity calibrated with fondaparinux.
Absolute bioavailability of 100% after subcutaneous administration; plasma peaks ~2–3 hours after dosing.
Predominantly renal excretion of unchanged drug; no significant hepatic metabolism.
Elimination half-life of 17–21 hours (allowing once-daily administration).
Medicines from the same therapeutic group (ATC classification) or the same pharmacological class.
