Low Molecular Weight Heparin

By Rania Gollakner, BS, DVM, MPH

What is low molecular weight heparin? 

Low molecular weight heparin (LMWH) is a broad category of anticoagulants derived from unfractionated heparin. It is available as many brand names (Lovenox, Fragmin, Innohep) and generic names (enoxaparin, dalteparin, tinzaparin). This form of heparin lasts longer in the body. It can be more easily administered at home and does not need the same level of monitoring as the unfractionated heparin. Heparin is used to prevent abnormal blood clots due to conditions such as heart disease.

Its use in cats, dogs, or horses to treat abnormal blood clots is ‘off label’ or ‘extra-label’. Many drugs are commonly prescribed for off label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions very carefully as their direction may be significantly different from those on the label.

How is LMWH given?

LMWH is given by injection under the skin (subcutaneously). Measure doses carefully and use a new needle and syringe for each injection. Do not shake the vial. Do not give this medication if discolored or has visible specks in the solution.

This medication should take effect within 1 to 2 hours; however, effects may not be noted outwardly and therefore laboratory tests may need to be done to evaluate this medication’s efficacy.

What if I miss giving my pet the medication?

If you miss a dose, give it when you remember. If it is close to the time for the next dose, skip the dose you missed and give it at the next scheduled time, and return to the regular dosing schedule. Never give your pet two doses at once or give extra doses.

Are there any potential side effects?

Studies in animals are limited for this medication and therefore information regarding side effects is also limited. In humans, side effects include pain at the injection site. More serious side effects may include excessive bleeding/hemorrhage, low blood cell counts, nausea, allergic reactions, and fever.

This short-acting medication should stop working within 24 hours, although effects can be longer in pets with liver or kidney disease.

Are there any risk factors for this medication?

Do not use LMWH in pets that are allergic to it, unfractionated heparin, or pork. Use cautiously in pets with liver or kidney disease. Use cautiously in pregnant or nursing animals, as safety has not been established.

Are there any drug interactions I should be aware of?

The following medications should be used with caution when given with LMWH: other anticoagulants, platelet-aggregation inhibitors, SSRIs, or thrombolytic agents.

Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.

Is there any monitoring that needs to be done with this medication?

Monitoring may include complete blood counts, urinalysis, and anti-Xa activity laboratory tests. Monitor for side effects including, severely low energy, trouble breathing, walking difficulty, or rear-limb paralysis, as this may indicate abnormal clot formation. Contact your veterinarian if these symptoms are noted.

How do I store LMWH?

Most formulations of LMWH should be stored at room temperature around 77°F (25°C). If already drawn into syringes, they may require refrigeration. However, there are many manufacturers of LMWH, and storage recommendations may differ, so always follow the storage instructions on the label.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, contact an emergency facility.

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