Clinical Context

Enoxaparin is an injectable low-molecular-weight heparin (LMWH), used as an anticoagulant to prevent thrombosis of the leg veins in patients who are on bed rest or who are undergoing hip replacement, knee replacement, or abdominal surgery. To treat deep vein thrombosis in the leg, the drug is often used with warfarin. It is also used in combination with aspirin to reduce complications from myocardial infarction.

Epidural or spinal anesthesia, spinal puncture, or epidural injection for pain in patients receiving an anticoagulant such as enoxaparin is associated with a risk for epidural or spinal hematoma. Such a risk could result in paralysis and/or other serious complications.

Synopsis and Perspective

The US Food and Drug Administration (FDA) released a drug safety advisory with recommendations aimed at reducing the risk of spinal column bleeding after spinal intervention, including epidural procedures and lumbar puncture, in patients taking LMWHs.

The agency is recommending that "health care professionals carefully consider the timing of spinal catheter placement and removal, and delay dosing of anticoagulant medications for some time interval after catheter removal," to decrease the risk of spinal bleeding and subsequent paralysis in these patients.

"These new timing recommendations, which can decrease the risk of epidural or spinal hematoma, will be added to the labels of anticoagulant drugs known as low molecular weight heparins, including Lovenox and generic enoxaparin products and similar products," the FDA said in the safety announcement.

Epidural or spinal hematomas are a known risk associated with enoxaparin in the setting of spinal procedures and are already included in a Boxed Warning and the Warning and Precautions sections of the labels for enoxaparin and generic enoxaparin products. "However these serious adverse events continue to occur," the FDA notes.

The drug manufacturer submitted 170 cases of spinal or epidural hematoma associated with enoxaparin thromboprophylaxis and neuraxial spinal or epidural anesthesia or spinal puncture reported between July 20, 1992, preceding FDA approval of Lovenox on March 29, 1993, and January 31, 2013.

"FDA reviewed these reports and found that 100 cases contained a confirmed diagnosis of spinal or epidural hematoma (by computed tomography [CT], magnetic resonance imaging [MRI], clinical symptoms/signs or surgical findings) or clear mention of spinal or epidural anesthesia, spinal puncture, or epidural anesthesia."

To address this safety concern, they note, the FDA worked with the drug manufacturer, "to further evaluate this risk and to update the Warnings and Precautions section of the Lovenox label with these additional time recommendations. The labels for generic enoxaparin products will be revised accordingly, as will those of other low-molecular-weight heparin-type products."

All anticoagulants carry this risk of causing spinal bleeding when used in conjunction with epidural/spinal anesthesia or spinal puncture. "We are continuing to evaluate the safety of other anticoagulants to determine if additional label changes are needed," the announcement notes.

Specifically, the FDA recommends that "health care professionals and institutions involved in performing spinal/epidural anesthesia or spinal punctures should determine, as part of a pre-procedure checklist, whether a patient is receiving anticoagulants and identify the appropriate timing of enoxaparin dosing in relation to catheter placement or removal. To reduce the potential risk of bleeding, consider both the dose and the elimination half-life of the anticoagulant:

• For enoxaparin, placement or removal of a spinal catheter should be delayed for at least 12 hours after administration of prophylactic doses, such as those used for prevention of deep vein thrombosis. Longer delays (24 hours) are appropriate to consider for patients receiving higher therapeutic doses of enoxaparin (1 mg/kg twice daily or 1.5 mg/kg once daily).
• A postprocedure dose of enoxaparin should usually be given no sooner than 4 hours after catheter removal.
• In all cases, a benefit-risk assessment should consider both the risk for thrombosis and the risk for bleeding in the context of the procedure and patient risk factors."

Clinical Implications

• A new FDA drug safety advisory regarding use of LMWHs in patients undergoing spinal intervention, including epidural procedures and lumbar puncture, offers new recommendations intended to reduce the risk of spinal column bleeding in these patients. Despite a Boxed Warning on the labels for enoxaparin and generic enoxaparin products (as well as information in the Warning and Precautions sections) concerning the risk for epidural or spinal hematomas, these adverse events continue to occur.
• The drug manufacturer submitted for FDA review 170 cases of spinal or epidural hematoma associated with enoxaparin thromboprophylaxis and neuraxial spinal or epidural anesthesia or spinal puncture. Of these, 100 cases had a confirmed diagnosis of spinal or epidural hematoma by CT; MRI; clinical symptoms/signs or surgical findings; or clear mention of spinal or epidural anesthesia, spinal puncture, or epidural anesthesia.
• The FDA recommends that clinicians and institutions involved in spinal or epidural anesthesia or spinal punctures use a preprocedure checklist to record use of anticoagulants and to identify the appropriate timing of enoxaparin dosing relative to catheter placement or removal. To lower the potential risk of bleeding, both the dose and the elimination half-life of the anticoagulant should be considered.

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