A New Blood Thinner to Prevent Stroke

A doctor reviewing MRI films. (iStockphoto)
A doctor reviewing MRI films. (iStockphoto)

It was only a year ago, I wrote about a new blood thinner (dabigatran) to prevent stroke in patients with irregular heart rhythm. Now we have a second drug (rivaroxaban) for the same indication. This is good news for patients who are on blood thinners like warfarin – a rat poison.

About 350,000 Canadians suffer from irregular heart rhythm called atrial fibrillation (AF). In the U.S. there are approximately 2.3 million adults with AF. The commonest cause of AF is getting old. The lifetime risk of getting AF is one in four after the age of 45. Before that it is not that common. Occasionally, you do see patients in their 20s and 30s.

Most common causes of AF are: hypertension, valvular heart disease, alcohol excess, thyroid disease, obesity, sleep apnea, genetic predisposition and it can be idiopathic (cause unknown). What I call GOK – God only knows!

The most dangerous complication of AF is stroke. It accounts for up to 36 percent of all strokes in elderly people. The cost of looking after patients with stroke runs into millions of dollars.

In order to prevent stroke, patients with AF are converted to regular (sinus) rhythm by applying direct-current electrical shock (cardioversion), by medications or by ablation therapy. If it is difficult to sustain regular rhythm, then the patients receive blood thinners (like warfarin) on a regular basis to reduce the risk of stroke by 70 percent.

The main advantages of warfarin are that it is cheap and is covered by provincial drug plan. Major disadvantages are that you need frequent blood tests to make sure that the blood concentration of the drug is at a safe level to keep the blood thin. But not dangerous enough to make you bleed in the brain or some other place. It is quite difficult to achieve the safe level and maintain it.

Over the years, there has been great amount of research to find a drug to replace warfarin. Last year, dabigatran (Pradax) was introduced. This year we have rivaroxaban (Xarelto) in the market. These new blood thinners do not require regular blood tests.

Rivaroxaban is an oral blood thinner invented and manufactured by Bayer as Xarelto. Rivaroxaban is well absorbed from the gut and maximum inhibition of factor Xa occurs four hours after a dose. The effects last eight to 12 hours, but factor Xa activity does not return to normal within 24 hours so once-daily dosing is possible. Compared to dabigatran which is to be taken twice a day. The daily dose for rivaroxaban is usually 20 mg once a day.

The newer oral blood thinners have been found to be better in preventing stroke than warfarin and the risk of side-effects like bleeding is less than warfarin. And remember – no blood tests.

There are two significant disadvantages to taking the newer drugs. One, there is no antidote to convert your blood to normal if you have a significant bleed after trauma or bleeding due to another cause. The mortality rate can be high. Second, the pills are expensive. So, you have to check with your insurance company if the cost of the pills will be covered. Xarelto is slightly cheaper than Dabigatran because of once a day dosage.

Now, only if we can permanently prevent atrial fibrillation, warts, common cold and hemorrhoids (just to mention a few) then life will be good. You won’t have to choose between the devil and the deep sea. But some of us will be out of business.

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