Drug update: Outpatient treatment of deep vein thrombosis.

Outpatient management with a low-molecular-weight heparin is the wave of the future for treating deep vein thrombosis. Already prevalent in Europe and Canada, a surge of outpatient programs in the United States is expected in the next 5 years.

Low-molecular-weight heparin (LMWH) is at least as effective and safe as unfractionated heparin for treating deep vein thrombosis. LMWH, delivered by subcutaneous injection, has greater bioavailability, a longer half-life, and greater predictability in dosing, compared with unfractionated heparin. Outpatient management with LMWH is also more convenient and less expensive. No regular laboratory monitoring is required with LMWH, except in morbidly obese patients and patients with renal failure. Unfractionated heparin is no longer considered standard care for this disorder in most patients.

Among patients needing treatment for deep vein thrombosis, approximately two-thirds will be eligible for outpatient therapy. The cost savings of an outpatient regimen may not be apparent to hospital administrators, and many insurance carriers may not pay for the injectable medication or for follow-up.

Initial treatment usually involves simultaneous use of warfarin and a low-molecular-weight heparin to get the patient's international normalized ratio (INR) to 2-3. After this ratio has been achieved for 2 consecutive days, usually after 5-7 days of therapy the LMWH is stopped and warfarin is continued, tyipically for about 6 months.

There is no good evidence that one LMWH is better than another. Formularies, price, and discounts are the main considerations. Adverse reactions are similar within the class. There is a very low incidence of bleeding (2%) and heparin-induced thrombocytopenia (1%). Local inflammation or bruising can occur at the injection site; these effects can be reduced by careful attention to detail during injection.

Outpatient treatment may not be appropriate for the elderly because they have a greater tendency to bleed while on anticoagulants and are more likely to have impaired renal function. It is also more difficult for elderly patients to give themselves injections. LMWHs appear to be safe and effective during pregnancy. Many practitioners are switching to LMWHs to treat pregnant women, but some use unfractionated heparin in anticipation of the substantial bleeding during delivery For outpatient treatment in pregnant women, use full doses but adjust as needed. Dosage usually needs to be increased during the third trimester. LMWHs appear to be safe in breast-feeding women.

 
Drug        Dosage              Cost/Day 
 
enoxaparin  1 mg/kg b.i.d. or   $85.72 
(Lovenox)   1.5 mg/kg once      (70-kg patient, 
            daily               b.i.d. dosage) (*) 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
dalteparin  100 IU/kg b.i.d or  $63.07 
(Fragmin)   200 IU/kg once      (70-kg patient) (*) 
            daily 
 
 
 
 
 
 
 
 
 
tinzaparin  175 IU/kg once      $51.45 
(Innohep)   daily               (70-kg patient) (*) 
 
 
 
 
 
 
 
 
 
 
warfarin    5 mg/day            $0.63 (**) 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Drug        Comment (+) 
 
enoxaparin  Only drug approved for outpatient 
(Lovenox)   treatment of deep vein ...