MONDAY, Nov. 14 (HealthDay News) -- Most people taking the blood-thinner warfarin need blood tests every four weeks to make sure they're receiving the right dose of medication, but new research suggests that some people could safely have those tests done just once every 12 weeks.
Longer intervals between monitoring isn't an option for everyone on warfarin, just those who have received the same dose of medication for six months or longer, noted the study, published in the Nov. 15 issue of the Annals of Internal Medicine.
"Sometimes it's difficult to go every four weeks, and we found that for patients who are very stable who have been monitored every four weeks, going every 12 weeks was not different in dosing," said the study's lead author, Dr. Sam Schulman, a professor of medicine and director of the clinical thromboembolism program at McMaster University in Hamilton, Ontario.
"Since there are 2 million patients in North America on warfarin, it could add quite a bit of cost savings if they could go longer [between tests]," said Schulman.
Warfarin (brand names Coumadin, Jantoven) thins the blood, and it's prescribed to help prevent blood clots. Blood clots can cause heart attacks and strokes. If too little warfarin is given, the blood isn't thinned enough and blood clots can form. But too much warfarin can thin the blood excessively, making internal bleeding a risk.
Once the right dose is found, some people remain stable on that dose indefinitely. For others, constant changes are needed to their warfarin dose. Schulman said that about one-third of his patients have stable doses.
The test that's done every four weeks to monitor a patient's warfarin dose is called international normalized ratio (INR) monitoring.
The current study included 250 people who were receiving unchanged warfarin doses for at least six months. They were randomly assigne
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