Treatment of
Thrombosis
Written by: Lisa Anselmo PharmD, BCOP
Editors: Stephan Moll, MD
Thrombosis is the medical term for an abnormal blood
clot in an artery or vein. The body’s ability to form blood clots its natural
defense against bleeding. Clots are formed through a series of chemical
reactions between special blood cells (platelets) and proteins (clotting
factors) in blood. The platelets and factors work together to regulate the
clotting process to start and stop clotting as the body needs it. Sometimes the
process does not work correctly, and a clot forms in blood vessels, blocking
blood flow to the surrounding tissues. There are two main types of clots. How
they effect the body depends on the type and location of the clot.
- Arterial thrombosis–the clot is in an
artery, usually in the heart or brain, and causes a heart attack or stroke.
-
Venous thrombosis–the clot is in a vein, usually one of the deep veins of the leg (deep vein thrombosis; DVT) and causes swelling and pain.
Clots can also break apart and travel to another part
of the body and cause another blockage. When this occurs, it is called an
embolus.
Heparin
Heparin is a strong, fast-acting anticoagulant (blood
thinner). It is usually given in the hospital by IV (a small needle inserted in
a vein), but it can also be given by an injection under the skin. IV heparin
works rapidly; within minutes of receiving it, most patients have excellent
anticoagulation that will prevent further clotting. However, patients who get
heparin must be monitored every day with a blood test to see if the correct dose
is being given. The doctor will adjust the dose of heparin according to the
blood test results. Because heparin levels often change in patients, the doctor
must check levels frequently. The name of the blood test used to check a
patient’s heparin level is the activated partial thromboplastin time (aPTT).
For patients who have a new clot, heparin is usually
given with another anticoagulant, warfarin (Coumadin®). Warfarin is
a pill that patients can take at home for long term anticoagulation. Because it
can take 5-7 days (or longer) for the warfarin to take effect, patients will
initially take both drugs. Once the warfarin is fully active, the heparin
is stopped and the patient can go home from the hospital.
The advantages of heparin are its low cost and fast
action (blood can be anticoagulated quickly). The disadvantages of heparin
include the need for frequent blood tests to check the levels of anticoagulation
and hospitalization to get an IV drug. Patients should expect to be in the
hospital 5-10 days to treat a new clot.
The most serious side effect of heparin is bleeding.
Other side effects include skin rash, headache, cold symptoms, and stomach
upset. A less common side effect is loss of bone strength if patients are on
heparin for long periods of time (usually months). This is generally only a
problem for pregnant women. A rare side effect of heparin is a condition called
Heparin Induced Thrombocytopenia (HIT). HIT is sometimes incorrectly called
“heparin allergy”. It occurs in a small number of patients, but it has very
serious symptoms including worsening of clotting and developing new clots, which
can lead to stroke, heart attack, deep vein thrombosis, and death.
Low Molecular Weight Heparins
Using LMWH has two advantages over heparin:
-
Patients can be treated at home, because
LMWH is given by an injection under the skin. This eliminates or reduces the
time patients need to spend in the hospital to treat their clot.
-
Patients
generally do not need to be monitored with a blood test when they are taking
LMWH.
The side effects of LMWH are very
similar to heparin; however, HIT and osteoporosis are much less common. LMWH is expensive.
Warfarin
Warfarin
(Coumadin®) is an anticoagulant pill that is taken by mouth.
Patients are given warfarin for different reasons.
Some patients may take warfarin for a few weeks; others will need to take
warfarin the rest of their lives. The
length of treatment depends on the reason why a patient needs anticoagulants.
Warfarin works by slowing down the
process in the liver that uses vitamin K to make certain proteins (clotting
factors) that cause clotting.
Because it may take several days before warfarin becomes completely effective,
heparin or LMWH is given until the warfarin is working.
As with patients who take heparin,
patients taking warfarin need to have their blood tested to see how well the
drug is working and to be monitored for safety. This blood test measures how
long it takes blood to clot, and is also called a prothrombin time, protime,
INR, or clotting time. Because
different labs use different methods to measure clotting time, the results of
the test can vary. To make sure a doctor can correctly interpret this test, the
results are reported with an INR number (International Normalized Ratio) that
converts all clotting times to the same number.
People who are not taking warfarin have an INR around 1.0 (usually
between 0.8 and 1.2). Most patients on warfarin should have an INR between 2 and
3; this is considered their therapeutic range. In some patients, a higher or
lower INR range is targeted. If a
patient has an INR that is below their therapeutic range, the risk of clotting
is higher; if a patient has an INR above the therapeutic range, the risk of
bleeding is higher. When patients
first start warfarin, they may get their blood tested two or three times a week.
Once patients are on a regular dose of warfarin, they may go as long as 4
weeks between blood tests.
Bleeding is the most common side effect
of warfarin. Other side effects
include headache, rash, hair loss, skin necrosis, purple toe syndrome, and
elevated liver enzymes. Sometimes
these side effects will go away over time; however, it is important to discuss
any of these side effects or unusual symptoms with your health care provider.
If the side effects do not go away, your doctor may prescribe a different
blood thinner.
Points to remember about taking
warfarin:
- Keep your diet consistent. Many foods, especially green vegetables,
have vitamin K in them.
- Tell the doctor, nurse, or pharmacist who is monitoring your INR if you
start a new medication. Some medications, especially antibiotics, can raise
or lower your INR. Over-the-counter anti-inflammatory medications (such as
aspirin or ibuprofen) may increase your risk of bleeding. You can usually
take acetaminophen (Tylenol®). But if you take acetaminophen
more than once a day and for longer than a week, you should tell the
provider monitoring your INR.
- Taking herbal medications while taking warfarin is discouraged. Many
herbal medicines will interact with warfarin and change your INR. Some of
these medications have anticoagulant properties and may put you at greater
risk for bleeding. Many herbal products do not list all of their ingredients
and may not work as advertised. If you must take an herbal medication, it
is important that the provider monitoring your INR knows what you are
taking.
- Take warfarin at the same time every evening. The evening is the best
time to take warfarin because any medication changes can be made during the
day. If you miss taking a dose of your warfarin, you have 8 hours to take
the medication; the dose should be skipped after 8 hours.
- Limit alcohol intake. Drinking a light or moderate amount of alcohol
(1-2 glasses of wine or 1-2 beers per day) usually does not influence the
INR and will not increase the risk for bleeding. However, drinking a large
amount can affect the way warfarin works and increase your risk for
bleeding.
The National Alliance for Thrombosis and Thrombophilia
(NATT) and its Medical and Scientific Advisory Board (MASAB) do not endorse or
recommend any commercial products, processes, or services. The views and
opinions of authors expressed on the NATT or MASAB websites or in NATT or MASAB
written materials do not necessarily state or reflect those of NATT or MASAB,
and they may not be used for advertising or product endorsement purposes.
It is not the intention of NATT or MASAB to provide
specific medical advice, but rather to provide users with information to better
understand their health and their diagnosed disorders. Specific medical advice
will not be provided and both NATT and MASAB urge you to consult with a
qualified physician for diagnosis and for answers to your personal questions.
Posted December 1, 2008
