Many patients taking the blood thinner warfarin have been told that it should be taken at night.
But in a new study, researchers found that the time of day doesn’t matter.
They found whether warfarin is taken in the morning, or the evening, its therapeutic effect is the same
The research was conducted by a team at the University of Alberta in Edmonton, Canada.
Warfarin is used to prevent blood clots that can cause strokes, heart attacks, and blockages. It is also used to treat the abnormal heart rhythm called atrial fibrillation.
The drug is difficult to take because it’s a drug that is so variable depending on what people eat, and what other medications they are taking.
Doctors have had a practical reason for telling patients to take warfarin in the evening.
Patients who use it must have blood tests every one to four weeks to determine if their dose is correct—too much can lead to bleeding, too little won’t prevent clots.
Taking the drug at night meant less time between getting a test result and adjusting the dose.
In the study, the team randomly assigned 217 patients to take their warfarin either in the morning or in the evening.
Over seven months, they tracked the amount of time patients’ blood levels were outside the range where warfarin is most effective.
They found no big difference in effectiveness was seen regardless of when the drug was taken.
The team says health care providers should stop telling patients to use their warfarin in the evening; rather, warfarin should be taken whenever regular compliance would be easiest for patients.
One author of the study is Dr. Scott Garrison, an associate professor of family medicine.
The study is published in the Annals of Family Medicine.
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