Taking care by taking charge

The effects of suffering a stroke aren’t all physical — depression and fear inevitably follow at some point. Usually, the fear is based on the not-unfounded possibility of having another, even more devastating stroke. In fact, people who’ve had a stroke are three times more likely to have a second stroke than they were to have one in the first place. Fortunately, people whose stroke was the result of complications from atrial fibrillation (AF) can do something positive to protect themselves.

For more than a decade, people with AF have reduced the risk of clot formation, lowering their risk of stroke, by taking – in pill form – an anticoagulant called CoumadinÒ (warfarin). The drug doesn’t “thin” the blood, but interferes with the functioning of Vitamin K in the clotting process, making it less likely that a dangerous clot will form and go on to cause a stroke.

CoumadinÒ has a “narrow therapeutic window” – a small difference between too high and too low a dose. Too much medication can lead to an increased risk of bleeding while too little can result in stroke or transient ischemic attacks. (Consired a “warning” stroke, a TIA’s stroke-like symptoms disappear within 24 hours.) Recognition of the importance of careful management of the drug’s narrow therapeutic range has grown since CoumadinÒ ’s approval in 1956, and it’s since been shown that lower doses than first introduced are both safer and just as effective.

A pharmacist and assistant professor in the Faculty of Pharmacy at the University of Toronto, Susan K. Steinberg, now 52, suffered a stroke in 1993. Early in her treatment she began taking CoumadinÒ . “I think it’s a wonderful drug if you need it,” she says, although she emphasizes the need for proper monitoring.

Blood tests measure prothrombin time (PT), the time required for the blood to clot. This is reported in a standardized form known as the International Normalized Ratio (INR), allowing comparison of PTs performed in diverse laboratories. Careful monitoring means a reduced risk of bleeding or conversely, reduced rate of stroke.

To allow doctors to provide patients with the dose right for them, the tablets are available in seven different measures from one to 10 mg.

Effective dosage is influenced by a number of factors, including the rate at which each body breaks down CoumadinÒ . “Any change in diet could affect how CoumadinÒ works in your body,” notes Steinberg. She eats a regular diet, including breads, meats, fish, dairy products, vegetables and fruits and avoids over-indulging, recognizing that the amount and types of food need to be regular.

“It’s important to not have a sudden change in your diet,” she says. “If you should start eating a lot of green, leafy vegetables, for example,” she says. “You will increase your levels of vitamin K which will counteract the effect of Coumadinâ .”

Consultation with physician or pharmacist is important before taking other drugs, even those bought over the counter, since a broad range of common drugs interacts with warfarin, increasing or decreasing clotting times. Extra monitoring of the INR may be necessary, for instance, when a patient has an infection and must take an antibiotic. Some other problematic drugs include barbiturates, oral diabetes agents, adrenocortical steroids, thyroid preparations, tamoxifen, acetominophen and non-steroidal anti-inflammatories such as ibuprofen. ASA can increase INR and may also lead to gastrointestinal bleeding. Even an ointment containing methylsalicylate applied to the skin can affect clotting times.

Herbal products must also be treated with caution. Ginkgo biloba, dong quai and ginseng have been reported as affecting INR. Among other herbal products affecting coagulation are arnica, evening primrose oil, ginger, willow, and chondroitin.

Sadly, in spite of the drug’s proven effectiveness, one third of the approximately 200,000 Canadians with atrial fibrillation aren’t receiving CoumadinÒ . Susan Steinberg, however, is glad she is doing something to safeguard her health and prevent another stroke. “I’m not afraid of the fact that I’ll be on CoumadinÒ for life,” she says. “It’s been around a long time, so we know lots about it. It’s helped a lot of people. It’s a great drug if it’s used properly.”