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Side Effects of


Home>Side Effects>Anticoagulants

“Anticoagulant” refers to a broad category of medications that include a number of different classes. They work to stop blood coagulation and the formation of a clot.
These pharmacological classes include:

  • Novel oral anticoagulants (e.g., Dabigatran)
  • Coumarin – Vitamin K Antagonists (e.g., Warfarin)
  • Heparin
  • Synthetic inhibitors of factor Xa (e.g., Idraparinux)
  • Direct factor Xa inhibitors. (e.g., Apixaban)
  • Direct thrombin inhibitors (e.g., Hirudin)
  • Antithrombin protein therapeutics
  • (Physicians’ Desk Reference, 70th Ed., 2016)

    Serious Side Effects of Anticoagulants

    Across these pharmacological classes which encompass anticoagulants, the most serious and common adverse reaction is uncontrolled bleeding, as detailed in British Journal of Clinical Pharmacology “Safety profile of the direct oral anticoagulants: an analysis of the WHO database of adverse drug reactions” (Jan 2017).

    Novel Oral Anticoagulants

    Novel oral anticoagulants have a faster onset than traditional drugs like Warfarin. Common side effects include:

  • Bleeding
  • Diarrhea
  • Nausea
  • Skin hemorrhage (can cause bruising)
  • Anemia
  • Wound secretion
  • Epistaxis (nosebleed)

    (Pharmacological Research, “Balancing thromboembolic and bleeding risk with non-vitamin K antagonist oral anticoagulants [NOACs]” January 2017)


    Coumarins are vitamin K antagonists. The most famous drug in this class is Warfarin. Side effects can be fatal and include:

  • Increased risk of bleeding (certain genetic variations of a gene called CYP2C9 have a higher risk of bleeding than those without the variation)
  • Paralysis
  • Paresthesia (pins and needles)
  • Headache
  • Arthralgia (Joint pain)
  • Muscle pain (Myalgia)
  • Dizziness
  • Shortness of breath
  • Hematomas
  • Spinal cord haemorrhage
  • Gastrointestinal haemorrhage
  • Intracranial haemorrhage
  • Skin necrosis (skin death)
  • Purple toe syndrome
  • Gangrene
  • Foot ulcers
  • Hypertension (high blood pressure)
  • (Current Hematology Reports “Risk factors for bleeding in patients taking coumarins” (Sep 2002); Clinical Hematology “First-generation agents: aspirin, heparin and coumarins,” Mar 2004)


    Heparin side effects include:

  • Haematomas
  • Melena
  • Hematuria
  • Epistaxis
  • Skin necrosis
  • Rash
  • Asthma
  • Rhinitis
  • Anaphylaxis
  • (Clinical Hematology “First-generation agents: aspirin, heparin and coumarins,” Mar 2004)

    Synthetic Inhibitors of Factor Xa

    Synthetic inhibitors of factor Xa, for instance Fondaparinux, are associated with the following common side effects:

  • Coma
  • Cardiac arrest
  • Haemorrhage (bleeding)
  • Hematoma (solid swelling of clotted blood)
  • (Cochrane Database Systematic Reviews “Factor Xa inhibitors for acute coronary syndromes,” Jan 2011)

    Direct Thrombin Inhibitors

    Direct thrombin inhibitors include Hirudin. Side effects include:

  • Haemorrhage
  • Hematoma
  • Anemia
  • Epistaxis (nosebleed)
  • (Therapeutische Umschau “New anticoagulants – direct thrombin inhibitors,” Nov 2012)

    Understand Your Risks with the Rxight® Genetic Test

    Many patients respond well to anticoagulant drugs, but a portion will find side effects – particularly the hematologic side effects – to be severe. This interpatient variability is partly due to genetically encoded differences in the ways drugs are metabolized.

    Rxight® DNA testing from MD Labs is designed to allow patients and their prescribers to understand how they might react to a drug – preferably before they begin treatment. Over two hundred prescription and OTC medications are tested based on a process called “SNP genotyping.” All that is required is a simple non-invasive cheek swab of your DNA. After the sample is processed at our labs, your results will be reviewed with you in detail.

    How Does Pharmacogenetic Testing Work?

    Genetic variations (called polymorphisms) in the genes that code for the enzymes and receptors that interact with anticoagulants can increase the probability of developing adverse effects. Identifying these polymorphisms can therefore reduce the likelihood of patients suffering from side effects. Physicians can prescribe a lower starting dose of the drug given certain alleles, or can move the patient to a different pharmacotherapy altogether.

    Contributors to this Article:
    Michael Sapko, MD, PhD; Deborah Kallick, PhD, Medicinal Chemistry

    Anticoagulants Tested Include:

    Read more about Rxight® Genetic Testing For Drug Metabolism