A typical use would be in treating dogs with autoimmune hemolytic anemia to reduce the potential for pulmonary thromboembolism. The pharmacology of the LMWH product seems to be different in sick dogs, as their response appears to be less predictable compared to healthy dogs, but still more predictable than UFH. It is unclear whether this could relate to their illness or variations in body fat. Sick dogs may need more enoxaparin to achieve the therapeutic range. Enoxaparin is expensive at ~$100/ml; the average size dog requires ~0.3 ml SQ q 6h. Dalteparin is comparably priced.

Other clinical indications: Not recommended for routine use for major orthopedic surgery, because thrombosis is usually subclinical. It could be helpful in acute glomerulonephritis, but the pharmacokinetics of medication need to be evaluated in dogs with low albumin. For treating disseminated intravascular coagulation, identifying and treating the underlying cause is still the primary objective. A low dose of UFH can be also used (50-75 U/kg SQ q 6-8h).

Suggested dosing for enoxaparin: In sick patients, a starting dose of 1 to 1.5 mg/kg q 6h SQ is cautiously suggested, based on the fact that unwell patients appear to need a slightly higher dose than healthy dogs. Requires factor Xa inhibition monitoring. As the pharmacologic response does not follow first kinetics, one cannot simply increase the dose by some multiple of the factor Xa inhibition level to achieve a predictably greater effect. Administer LMWH for 2 weeks beyond discharge. This is a practical compromise designed to minimize owner expense, although the risk of pulmonary thromboembolism may not have completely abated by 2 weeks.

Giving LMWH q 8h is probably a reasonable compromise if the q 6h regimen is impractical, but it does sacrifice some antithrombotic effect.

There are no pharmacokinetic data on use of LMWH in cats, but as an alternative Plavix® may work in cats. However, low dose aspirin seems to be as good as any other anticoagulant medication tried for prophylaxis of aortic thromboembolism.

[Contributed by Drs. Andrew Mackin and Kari Lunsford, Mississippi State University]