Dangers of Warfarin

7/29/2019 Dangers of Warfarin

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Dangers of warfarin

Take care with Warfarin. Warfarin is an oral anticoagulant - in other words Warfarin is a drug taken by

mouth used to prevent blood clotting. It used to be known as a rat poison - give rats a lot of Warfarinand they suffer death from internal bleeding.

So did Donald Dewar, the most senior government figure in Scotland and member of the Labour

Cabinet, who die on 11 October 2000, mourned across Briatin. He suffered a fatal brain haemorrhage

following a fall, after recent surgery to replace an aortic heart valve. The Warfarin successfully

prevented clots on the valve, but the Warfarin also thinned his blood, probably made the bleed worse

and made it even more difficult for surgeons to operate.

Warfarin works by blocking the creation of Vitamin K - vital to normal blood clot formation. Warfarin is

usually very safe when used carefully but the level in the blood is critical. Too much Warfarin and you

can bleed to death - as simple as that. Too little Warfarin and you could have, for example, a life-

threatening clot such as a deep vein thrombosis resulting in a pulmonary embolus (clot passing from leg

to lung).

The trouble is that Warfarin levels are affected by a huge number of other drugs that people may be

taking at the same time. These other drugs affect Warfarin levels by slowing or speeding up the rate of

Warfarin destruction by the liver, or by releasing more free Warfarin into the blood (usually quite a lot

of Warfarin is bound to proteins in the plasma), or by blocking absorption of Vitamin K, or by blocking

Vitamin K production by bacteria in the gut. Here are some examples of how Warfarin dose may need

to be adjusted:

Warfarin effect is increased by:

bullet Phenylbutazone

bullet Alcohol

bullet Anabolic steroids

bullet Chloramphenicol


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bullet Sulphonamides

bullet Colchicine

bullet Reserpine

bullet Mefanamic acid

bullet Aspirin

bullet Phenytoin

bullet Broad spectrum antibiotics

bullet Erythromycin

bullet Liquid paraffin

bullet Clofibrate

Warfarin effect is reduced by

bullet Barbiturates

bullet Rifampicin

bullet Oral contraceptives

bullet Glutethimide

bullet Griseofulvin

Weight changes and changes in kidney function can also affect Warfarin levels.

A common problem can be if a person is stable for a long time on Warfarin with a combination of other

drugs - but then one or two of the other drugs are stopped, perhaps sending Warfarin levels sky high or

perhaps far too low.


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A common early sign of Warfarin overdose is spontaneous bruising - patches of skin discolouration

without a history of injury, or even blood in the urine. The treatment of too much Warfarin is an

injection of Vitamin K which usually begins to act within 4 hours.

Blood-thinning drug warfarin may raise risk of death from brain haemorrhage

People who regularly take the blood-thinning drug warfarin may be doing themselves more harm than

good because it can increase the risk of death from a brain haemorrhage.

A new study has discovered that the drug, which is taken by hundreds of

thousands of patients at risk from a blood clot, may increase bleeding and so therisk of death during a haemorrhage in the brain.

The research carried out in the United States found that those taking the drug had twice as much

bleeding when they did suffer a stroke. This in turn led to a greater risk of death unless treated quickly.

Warfarin, for which there were 6.6 million prescriptions issued by the NHS in 2006, is taken by people at

serious risk from an eschemic stroke caused by a blood clot in the brain which blocks a blood vessel andstarves the brain of oxygen.

It is also effective in combating an abnormal heart rhythm called atrial fibrillation.

But the new research from the University of Cincinnati and published in the American academy of

Neurology journal shows that its blood-thinning properties can actually increase the danger from a

different sort of haemorrhagic stroke where a blood vessel bursts.

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Scientists led by Dr Matthew Flaherty used brain scans and found that if the drug makes the blood too

thin, it can increase the risk of brain haemorrhage, a type of stroke caused by bleeding in the brain.

"Warfarin is very effective for preventing ischemic strokes among people with atrial fibrillation and for

most patients with this condition it is the right choice," said Dr Flaherty.

"However, people who have bleeding into the brain while taking warfarin are at greater risk of dying

than other people with haemorrhagic stroke.

"This shows the importance of good monitoring and adjustment of warfarin dose. People should talk totheir doctors about the proper management of warfarin and learn the signs of stroke so they can get to

an emergency room immediately if a stroke occurs."

The study involved 258 people who had brain haemorrhage, 51 of whom were taking warfarin.

Participants were 69 years old on average and lived in or near Cincinnati.

The group underwent brain scans to confirm the type of stroke. The brain scans were used to measure

the size of the blood clots.

The study found that people who took warfarin and suffered a brain hemorrhage had about twice as

much initial bleeding as those not taking warfarin.

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Dangers of Warfarin