Blood Relations

People Taking Anticoagulant Drugs Should Be Educated About the Medications to Achieve Positive Results and Combat Adverse Outcomes

by Alexis Bergen

When a large number of cows mysteriously started bleeding to death in the early 20th century, two veterinarians investigated the phenomenon and found that the cows had been eating spoiled sweet clover.


Upon decomposition, sweet clover produces a substance called dicumarol, which contains natural anticoagulant properties. By disrupting the balance of clotting factors in the bloodstream, large quantities of dicumarol were deemed the culprit in the cattle hemorrhaging.


This discovery paved the way for the creation of warfarin—brand name Coumadin—a derivative of dicumarol and currently one of the most widely prescribed drugs in the United States.


For the last 40 years, warfarin has been used safely and effectively to prevent stroke and treat deep vein thrombosis (clots in the legs), pulmonary embolism (clots in the lungs) and other disorders related to abnormal clot formation. Patients also typically receive anticoagulant therapy after heart and orthopaedic surgeries.


Because anticoagulants interfere with normal clotting mechanisms, pharmacists and physicians carefully monitor patients taking drugs that affect coagulation to combat adverse complications and achieve positive outcomes. Patients should also be well educated about possible side effects, drug interactions and the importance of close medical supervision.


“It is important to empower patients with knowledge about their anticoagulant medication,” says May Mak, Pharm.D., assistant professor of pharmacy at the USC School of Pharmacy. “Patients need to be aware of danger signs in order to seek help before there is a major problem.” Mak says patients should contact their physician if they experience extensive bleeding, bruising, black stool, dark blue discoloration on the feet or any new skin lesions.


Clot Not
When cut or scratched, the human body stops the bleeding by developing a clot at the skin’s surface. However, blood that is continually moving throughout the body should not clot.


If an abnormal clot develops, there is potential for the clot—or thrombus—to break off and travel to the brain or lungs, depending on where the thrombus forms in the body.


“A clot that forms in the heart chamber can break off and travel to the brain, causing a stroke,” says Gladys Mitani, Pharm.D., associate professor of pharmacy at the USC School of Pharmacy. “A clot that develops in the lower leg often travels to the lungs, causing a life-threatening complication known as pulmonary embolism.”


Anticoagulant drugs help prevent harmful clots from forming by decreasing the blood’s ability to clot. A common misconception is that the drugs work by thinning your blood, says Mitani, who manages the Outpatient Cardiac/Anticoagulation Clinic at the LAC+USC Medical Center.


“Anticoagulants interfere with the normal clotting mechanism and intentionally prevent coagulation to a specific degree,” Mitani says. “It is a delicate balance; you don’t want to completely eliminate the patient’s ability to clot, which can increase the risk of bleeding complications.”


Currently, there are two major types of medications used for anticoagulation: drugs that are administered orally and drugs that are administered intravenously or by subcutaneous self-injection.
“Warfarin interferes with the production of four vitamin K-dependent clotting factors,” Mitani says. “Patients must take the warfarin for four to five days to reach a therapeutic state. In the same manner, it takes four to five days to reverse the process.”


Vitamin K, found in green, leafy vegetables, facilitates the activation of certain clotting factors that are essential for coagulation. “A patient with a diet high in vitamin K can decrease the therapeutic affect of warfarin. It is preferable for patients taking warfarin to maintain a balanced diet and eat the same amount of green vegetables every day,” she says.


A patient’s response to warfarin may be altered by many different factors including health status, diet, interaction with other medications and compliance with the drug regimen. A blood test is performed to ensure that the patient is maintaining a therapeutic level of warfarin.


“Patients should be monitored about once a month if well controlled and stable, and much more frequently if they are not,” Mitani says.


Stop the Clot
Because it takes up to four to five days for warfarin to begin working, patients who require immediate anticoagulation are often started on a form of heparin. Traditional heparin is usually administered intravenously, while the newer low molecular weight heparins are administered by subcutaneous injection.


“Heparin inhibits the production of factors that are essential in clot formation by binding to components in the blood,” says Pam Pickens, Pharm.D., adjunct assistant professor of pharmacy at the USC School of Pharmacy.


According to Pickens, who runs the Inpatient Anticoagulation Service at the LAC+USC Medical Center, heparin is trickier than warfarin to monitor. “Although there are effective tests used to measure levels of heparin, a lot of factors can change the readings.”


The most important complication associated with both warfarin and heparin is bleeding. “Patients on anticoagulants have to be especially careful when undergoing invasive procedures or major surgeries,” Mitani says. “Warfarin may be stopped four to five days prior to an invasive procedure to ensure a normal coagulation status at the time of the procedure.”


She adds, “To minimize the risk of thrombosis, patients are given heparin because of its short action and immediate onset. The use of heparin allows immediate reversal of anticoagulant effect before and immediate reinstitution of anticoagulation after surgery.”


Education and compliance remain major obstacles for patients, which is why anticoagulation clinics staffed by experienced pharmacists are becoming increasingly popular. Mitani stresses that when a patient begins anticoagulant therapy, it is critical that they receive proper education.


She says. “I remind patients to keep regular clinic appointments and continue with close medical supervision to minimize the risks of complications associated with warfarin as well as clot formation.”
And don’t eat the clover.