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Enoxaparin Side Effects

In Summary

Commonly reported side effects of enoxaparin include: anemia and hemorrhage. Other side effects include: fever. See below for a comprehensive list of adverse effects.

For the Consumer

Applies to enoxaparin: injectable, solution

In addition to its needed effects, some unwanted effects may be caused by enoxaparin. In the event that any of these side effects do occur, they may require medical attention.

Major Side Effects

You should check with your doctor immediately if any of these side effects occur when taking enoxaparin:

More common:
  • Bleeding gums
  • coughing up blood
  • difficulty with breathing or swallowing
  • dizziness
  • headache
  • increased menstrual flow or vaginal bleeding
  • nosebleeds
  • paralysis
  • prolonged bleeding from cuts
  • red or black, tarry stools
  • red or dark brown urine
  • shortness of breath
Less common:
  • Bruising
  • chest discomfort
  • collection of blood under the skin
  • confusion
  • continuing bleeding or oozing from the nose and/or mouth, or surgical wound
  • convulsions (seizures)
  • fever
  • irritability
  • lightheadedness
  • lower back pain
  • pain or burning while urinating
  • swelling of the hands or feet
  • tightness in the chest
  • uncontrolled bleeding at the site of injection
  • vomiting of blood or material that looks like coffee grounds
  • wheezing
  • Back pain
  • burning, pricking, tickling, or tingling sensation
  • chest pain
  • chills
  • cough
  • decreased urine output
  • dilated neck veins
  • dizziness or lightheadedness when getting up suddenly from a lying or sitting position
  • extreme fatigue
  • fainting
  • fast or irregular heartbeat
  • general feeling of discomfort or illness
  • irregular breathing
  • leg weakness
  • problems with bowel or bladder function
  • skin rash or hives
  • sneezing
  • sore throat
  • sudden fainting
  • swelling of the face, fingers, feet, genitals, mouth, or tongue
  • thickening of the bronchial secretions
  • troubled breathing
  • weight gain
Incidence not known:
  • Abdominal or stomach pain
  • deep, dark purple bruise
  • hives or welts
  • irregular heartbeat
  • itching, pain, redness, or swelling
  • large, flat, blue, or purplish patches in the skin
  • nausea or vomiting
  • nervousness
  • numbness or tingling in the hands, feet, or lips
  • puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
  • redness of the skin
  • skin rash
  • unusual tiredness or weakness
  • weakness or heaviness of the legs

Minor Side Effects

Some of the side effects that can occur with enoxaparin may not need medical attention. As your body adjusts to the medicine during treatment these side effects may go away. Your health care professional may also be able to tell you about ways to reduce or prevent some of these side effects. If any of the following side effects continue, are bothersome or if you have any questions about them, check with your health care professional:

Less common:
  • Diarrhea
  • irritation, pain, or redness at the place of injection

For Healthcare Professionals

Applies to enoxaparin: injectable solution


Hematologic side effects including wound hematoma (11%), anemia (3%), ecchymosis (3%), thrombocytopenia (1.5%), thrombocytosis, hemarthrosis, thrombosis, hypochromic anemia, and retroperitoneal hematoma have been reported. Clinical trials experience included reports of spinal/epidural hematoma and increased risk of hemorrhage. Postmarketing side effects have included hemorrhagic anemia and eosinophilia.[Ref]

Patients undergoing spinal/epidural anesthesia or puncture and anticoagulated or scheduled to be anticoagulated with low molecular weight heparins or heparinoids are at risk for long-term or permanent paralysis due to epidural or spinal hematoma. The risk of these events is increased by the use of indwelling epidural catheters or by concomitant use of platelet inhibitors, other anticoagulants, or drugs that affect hemostasis.

In one clinical study, compared with younger patients, the incidence of bleeding complications was higher in patients greater than or equal to 65-years-old.

Patients previously exposed to unfractionated heparin or a low-molecular-weight heparin appear to be more susceptible to developing heparin-induced thrombocytopenia (HIT) and HIT-related thromboembolic complications (e.g., transient ischemic attack, stroke) than those who were never exposed.

Heparin-induced thrombocytopenia (HIT) is an immune-mediated, prothrombotic reaction that occurs in 0.5% to 5% of patients treated with unfractionated heparin and in less than 1% of patients treated with a low molecular weight heparin (LMWH). The decrease in platelet count associated with HIT usually begins 5 to 14 days after starting heparin. However, patients with a previous exposure to heparin may have an abrupt decrease in platelets upon restarting heparin. Patients with LMWH-induced HIT exhibit a longer delay in the onset of symptoms compared with those who develop it from unfractionated heparin. Following discontinuation, platelet counts begin to recover within 4 days, but may take more than 2 weeks in patients with high-titer HIT antibodies. Thrombocytopenia is caused by heparin-dependent IgG antibodies that bind to a specific platelet protein, platelet factor 4 (PF4). The heparin-PF4-IgG immune complex binds to platelets causing platelet activation. The activated platelets cause release of platelet-derived procoagulant microparticles, which accelerate coagulation reactions and generate thrombin. LMWHs have a high cross-reactivity with circulating heparin-PF4-IgG immune complex. Factors associated with a higher risk for developing HIT-associated thrombosis include women, nonwhites, severity of thrombocytopenia, and lower body weight. Complications associated with HIT include exacerbation of venous thromboembolism, arterial or venous thrombosis, limb gangrene, stroke, and skin necrosis. The antibodies that cause HIT will usually disappear after approximately 3 months; therefore, use of unfractionated heparin or LMWH may be considered in a patient with a history of HIT if the antibody test is negative.

Factors associated with an increased risk of bleeding include high doses, advanced age, renal dysfunction, and concomitant use of other drugs that affect hemostasis.[Ref]


Hepatic side effects have included transient elevations in liver function tests. Postmarketing side effects have included hepatocellular and cholestatic liver injury.[Ref]


Local side effects have included pain, erythema, ecchymosis, and hematoma. Rarely, painful, red induration and necrotic ulcerations at the injection site have been reported. Skin necrosis distant from the injection site has also been reported.[Ref]

Skin necrosis occasionally accompanies heparin-associated thrombocytopenia and thrombosis syndrome. This complication is thought to occur less with enoxaparin than with unfractionated heparin. However, a recent report noted the occurrence of skin necrosis and associated thrombocytopenia with low molecular weight heparin use. If late-onset skin necrosis, thrombocytopenia, and/or thromboembolism occur during use, immediate discontinuation of low-molecular weight heparin is mandatory in order to avoid potentially fatal thromboembolic complications.[Ref]


Hypersensitivity side effects including systemic allergic reactions, pruritus, urticaria, and anaphylactic/anaphylactoid reactions including shock have been reported in postmarketing experience. A case of angioedema has been reported.[Ref]


Dermatologic side effects have included vesiculobullous rash, purpura, and cutaneous vasculitis. At least two cases of bullous pemphigoid-like eruption and one rare case of enoxaparin-induced ischemic skin necrosis have been reported. Postmarketing side effects have included alopecia.[Ref]


Respiratory side effects have included lung edema, pneumonia, and dyspnea.[Ref]


Cardiovascular side effects have included atrial fibrillation, heart failure, edema, and peripheral edema.[Ref]


Gastrointestinal side effects have included nausea and diarrhea.[Ref]


Metabolic side effects have rarely included hyperlipidemia. Postmarketing reports have included cases of hyperkalemia. Most of these reports occurred in patients who also had conditions that tend toward the development of hyperkalemia (e.g., renal dysfunction, concomitant potassium-sparing drugs, administration of potassium, and hematoma in body tissues).[Ref]

One case of hyperlipidemia with marked hypertriglyceridemia was reported in a diabetic pregnant woman, although causality has not been determined.[Ref]


Genitourinary side effects have included hematuria.

Nervous system

Nervous system side effects have included confusion and postmarketing reports of headache.


Other side effects have included fever.[Ref]


In general, hemorrhagic side effects have occurred in 3% to 7% of patients. A meta-analysis of published studies reported an overall incidence of major bleeding with low molecular weight heparins of 0.7% to 1.4%. Hemorrhage may occur at any site in the body.[Ref]

Any unexplained decrease in blood pressure and/or hematocrit as well as unexplained symptoms should prompt consideration of a possible hemorrhagic event.[Ref]


In a study involving pregnant women (n=120) requiring thromboprophylaxis, clinically significant bone loss (i.e., 10% or greater) in the femur occurred in approximately 2% to 2.5% of patients regardless if they received enoxaparin (68.4 mg/day) or unfractionated heparin (17,380 units/day) for approximately 26 to 27 weeks.[Ref]

Musculoskeletal side effects have included osteoporosis.[Ref]


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Not all side effects for enoxaparin may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.