Lovenox, or enoxaparin, is a so-called „low molecular weight heparin.” The old standard of therapy for a DVT was the intravenous infusion of standard heparin. Standard heparin could also be given as an injection, but it required 3 times a day injection of high volumes. Lovenox is an administered twice daily with injection. It has been demonstrated to reduce the risk of DVT during certain operative procedures when used prophylactically. Also, it is indicated for the treatment of DVT as an inpatient or outpatient. It is also indicated for patients with certain types of heart attacks known as „non-Q wave ischemic MI” or unstable angina (heart pains) in conjunction with aspirin.
HOW IS LOVENOX ADMINISTERED? WHAT IS THE DOSAGE?
Lovenox is given as a subcutaneous injection. The dosage administered depends on the reason it is being given and the patient’s health. In general, for prophylaxis to prevent blood clots forming during the surgery, the dose of Lovenox is 40 mg daily. Ideally, the first dose would be given 2 hours before the surgery is to take place. A daily dose of 40 mg daily is then given until the patient is over their „high risk” period. More on that topic later.
For the treatment of a DVT and/or PE, the dose of Lovenox is 1 mg per kg of body weight, twice a day. For example, if a patient with a DVT weights 100 kg, then the dose of Lovenox is 100 mg administered as a subcutaneous injection twice daily. The Lovenox is given until the Coumadin effects are at the desired level. There are circumstances where Coumadin cannot be used. A classic example is when a woman develops a DVT during pregnancy. Coumadin cannot be used to treat the DVT during pregnancy since it can have effects on the normal development of the baby. In that situation, Lovenox is continued until after delivery of the baby. For patients with kidney function impairment, the dose of Lovenox for prophylaxis is reduced to 30 mg subcutaneously daily.
HOW DOES LOVENOX WORK? HOW IS THE DOSE MONITORED?
The exact mechanism of how Lovenox works is not entirely understood. It is thought it acts with a blood protein called antithrombin III to neutralize activated Factor X, which by itself tends to promote clotting. There are no tests to measure the effects of Lovenox, as there are with heparin and Coumadin. However, one of the side-effects of Lovenox is lowering of the platelet count, the particles in the blood that become part of the blood clot. Therefore, the platelet count needs to be monitored while on Lovenox ( as well as heparin).
WHAT ARE THE SIDE-EFFECTS OF LOVENOX?
Lovenox is given as an injection underneath the skin in the subcutaneous tissue. It can cause a local irritation at the site of injection, with redness and itching. One can also develop bruising or a hematoma at the site of the injection. Rarely, one can have significant bleeding from another site, such as the intestinal tract. The use of spinal or epidural anaesthetic techniques is contraindicated in the event a patient is on Lovenox, for fear of bleeding into or around the spinal cord. Lovenox cannot be used in patients with a heparin allergy, or allergy to pork products.
As we mentioned previously, sometimes the platelet count can drop with Lovenox, and it often returns to normal with discontinuation of the Lovenox. Rarely, there is a very serious but infrequent side-effect of Lovenox called „Heparin-induced thrombocytopenia (HIT)” that is a very dangerous event. This type of event occurs more often with the use of regular heparin. HIT is a syndrome where the body develops antibodies to the heparin or Lovenox, resulting in paradoxical clotting inside the vessels, typically the arteries. there is a rapid decrease in the platelet count, couples with clotting in the arterial blood vessels leading to loss of tissue and limb. This disorder is very rare with Lovenox but can be devastating when it occurs.