What are anticoagulants?
An anticoagulant is a drug (blood thinner) that treats, prevents, and reduces
the risk of blood
clots-breaking off and traveling to vital organs of the body, which can lead
to life threatening situations. They work by preventing blood from coagulating
to form a clot in the vital organs such as the heart,
lungs, and brain.
For example, a DVT or
deep vein
thrombosis (blood
clot in the leg or lower extremity) can happen if you have a medical
condition that keeps you immobile or if you have been sitting for n long period
of time without getting up and stretching, like traveling by plane, car, or
train. If the clot breaks off from the vein or artery of a leg it can get lodged
in the blood vessels of the lung where it can form a clot in the lung (pulmonary
embolism). This is a life threatening medical condition. Similarly, a
stroke can be caused by a clot lodged in a vessel in the brain.
Anticoagulant treatment is used to prevent the formation of new blood clots,
and to treat existing clots by preventing them from growing larger in size. It
also reduces the risk of embolization of blood clots to other vital organs such
as the lungs and brain.
Why are they used?
An anticoagulant medicine is used in patients to prevent blood clots from
forming in veins, arteries, the heart, and the brain of a patient. For example,
if the clot travels to the patient's heart it can cause a
heart attack
or if one forms in the brain it may cause a
stroke or
TIA (mini-stroke, transient ischemic attack).
Examples of diseases and health conditions that require treatment with
anticoagulants to reduce the risk of clots forming, or are used to prevent
life-threatening problems include:
- Deep vein thrombosis (DVT)
- Heart attack
- Stroke
- For the prevention or treatment of:
- Pulmonary embolism
- Blood clots within venous and arterial catheters
- Stent
thrombosis - Blood clots during
atrial
fibrillation (afib) treatment
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List of anticoagulant side effects
The most common side effect of treatment with anticoagulant medicine is
bleeding. Treatment with these products may cause various degrees of bleeding,
including fatal bleeds.
This list of adverse effects associated with anticoagulants are compiled from
adverse effects listed for various anticoagulants and may not apply to every
medicine.
Common side effects include:
- Bleeding
- Abdominal pain
- Flatulence (intestinal gas)
- Headache
- Lethargy
- Dizziness
- Fever
- Local injection site reactions
- Nausea
- Anemia
- Bruises caused
by
trauma (ecchymosis) - Diarrhea
Other side effects include:
- Hair loss
(alopecia) - Rash
- Itching (pruritus)
- Changes is sense of taste
- Fainting
(syncope) - Shortness of breath
- Low blood
pressure (hypotension) - Chest pain
Serious side effects include:
- Cholesterol embolus syndrome
- Intraocular hemorrhage
- Groin hemorrhage
- Tissue necrosis
- Hematuria
- Anemia
- Hepatitis
- Respiratory tract bleeding
- Hypersensitivity reaction
- Hemorrhagic stroke
- "Purple toe" syndrome
- Increased
fracture risk with long-term usage
- Calciphylaxis
- Elevation of serum aminotransferases
- Thrombocytopenia
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Drugs and herbal supplements that interact with anticoagulants
Treatment with more than one blood thinner or using medicine that can cause
bleeding will increase the risk of bleeding from any anticoagulant. Examples of
drugs that also can cause bleeding when they interact include:
- Antiplatelet medicine such as
aspirin
and other nonsteroidal anti-inflammatory medications (for example,
ibuprofen [Motrin],
naproxen [Aleve]),
clopidogrel (Plavix),
and prasugrel (Effient) - Serotonin reuptake inhibitors (SSRIs) such as
fluoxetine (Prozac)
and paroxetine (Paxil). - Garlic and
ginkgo also increase the risk of bleeding when combined with another
medicine that thins the blood because these herbs can cause bleeding when taken
alone. - Drug and herbal supplement interactions with warfarin
Several
drugs may increase or decrease the anticoagulant effect of
warfarin
(Coumadin, Jantoven) therapy. Drugs that increase warfarin's anticoagulating
effect by reducing its breakdown include:
- amiodarone (Cordarone)
- trimethoprim/sulfamethoxazole
(Bactrim) - fluconazole
(Diflucan) - itraconazole
(Sporanox) - fluvastatin
- fluvoxamine
- metronidazole
miconazole - voriconazole (Vfend)
- zafirlukast
(Accolate) - ciprofloxacin
(Cipro) - cimetidine
- atorvastatin
(Lipitor) - clarithromycin (Biaxin)
- fluoxetine (Prozac)
- indinavir (Crixivan)
- ritonavir (Norvir)
Some drugs and herbal products that may reduce the anticoagulating effect of
warfarin by increasing its breakdown include:
- St. John's wort
- carbamazepine
(Tegretol,
Tegretol XR,
Equetro,
Carbatrol) - rifampin,
bosentan (Tracleer) - prednisone
Use of Warfarin with foods high in Vitamin K
Foods with high vitamin K content (for example, green leafy vegetables)
reduce the anticoagulant effect of warfarin. It's important for patients to try
to consume a consistent amount of vitamin K containing foods to avoid
fluctuations in the effect of warfarin. A patient that regularly consumes high
vitamin K containing foods may require a higher dose of Jantoven or Coumadin to
achieve the desired level of anticoagulation.
Are anticoagulants, aspirin, and antiplatelets the same type of drug?
No. Anticoagulants and antiplatelets differ in how they work. Anticoagulants
prevent blood coagulation by reducing the action of clotting factors directly or
indirectly. Antiplatelets work by inhibiting the ability of platelets to
participate in the clotting process. Aspirin is an example of an antiplatelet
medication.
Who shouldn’t take anticoagulants?
Anticoagulation therapy is not recommended for patients with certain diseases
or health conditions because they increase the risk of bleeding. Patients who
have any of the following health problems or are
pregnant
shouldn't use this type of therapy.
- Hemophilia or
another bleeding disorder - Are pregnant
- High risk of bleeding in the brain (hemorrhagic stroke)
- Cerebral aneurysm
- Dissecting aorta
- Pericarditis
- Pericardial effusion
- Bacterial
endocarditis - Active ulceration
- An active bleed
- Are undergoing surgery
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Different types or classes of anticoagulants
There are different types of anticoagulants, and they are classified by how
they affect the normal coagulation pathway (see the mechanism of action
section). The different classes are:
- Vitamin K antagonists (coumarin anticoagulants)
- Low molecular weight heparins (LMWH)
- Direct thrombin inhibitors
- Factor Xa Inhibitors
List of brand and generic names, and preparations (oral, injection, tablet, pill, powder)
Vitamin K antagonists
- warfarin (Coumadin, Jantoven) – oral tablets
Low molecular weight heparins (LMWH) and heparin (vials and syringes)
- enoxaparin (Lovenox)
- dalteparin (Fragmin)
- heparin
Thrombin inhibitors
- bivalirudin (Angiomax) – powder for injection
- argatroban (Acova) – injection
- dabigatran (Pradaxa) – oral capsule
- antithrombin III (Thrombate III) – powder for injection
Factor Xa Inhibitors (These are relatively new anticoagulants)
- apixaban (Eliquis) – oral tablets
- fondaparinux (Arixtra)
– injection - rivaroxaban
(Xarelto) –
oral tablets - edoxaban (Savaysa) – oral coated tablets
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Is it safe to take an anticoagulant if I’m pregnant or breastfeeding?
Most anticoagulants have not been adequately studied in patients who are
pregnant because
clinical trials
exclude them. Therefore, this type of therapy generally is avoided during
pregnancy and should be used during pregnancy only if the potential health
benefit justifies the potential dangers to the fetus.
Warfarin, specifically, is a medication that should be avoided if you are
pregnant or are planning to become pregnant.
Birth defects
and fetal bleeding have been reported during this type of therapy when taken
during pregnancy. Be careful to not get pregnant if you are currently on this
type of therapy. If you do become pregnant or are
trying to
conceive contact your doctor immediately.
Enoxaparin is an anticoagulant medicine that does not cross the placenta and
shows no evidence of effects on the fetus. It is often recommended by doctors
for patients who are pregnant as an alternative to oral therapy with warfarin,
which cannot be safely used during pregnancy.
There is little data about the excretion of this medicine in
breast milk.
Available evidence suggests that warfarin is not secreted in breast milk. Since
most medicines are excreted in breast milk, medical experts generally
recommended that if you are receiving this type of therapy you should not
breastfeed.
Anticoagulant mechanism of action (how they work)
How vitamin K antagonists (warfarin) cause anticoagulation
Warfarin prevents the formation of a
blood clots in patients by reducing the production of factors II, VII, IX,
and X, and the anticoagulant proteins C and S by the
liver. These factors are involved in the body's natural clotting process.
The production of these factors by the liver are dependent on adequate amounts
of vitamin K. Warfarin reduces the production of the factors because it
antagonizes vitamin K. The dose of warfarin is carefully adjusted to achieve
optimal anticoagulation while minimizing the risk of bleeding.
How low molecular weight heparins (LMWH) and heparin cause anticoagulation
Heparin and low molecular weight heparins prevent a blood clot from forming
by blocking the action of two of the 12 clot-promoting proteins in the blood
(factors X and II) whose action is necessary for blood to clot. Low molecular
weight heparins are produced by chemically breaking heparin into smaller-sized
molecules. Unlike heparin, medical professionals do not monitor the effect of
low molecular weight heparins with blood tests and the dose of a low molecular
weight heparin is not titrated.
How thrombin inhibitors cause anticoagulation
Thrombin inhibitors work by blocking the action of thrombin, a protein that
is necessary for the coagulation of blood and formation of a blood clot.
Reducing the action of thrombin reduces the ability of blood to clot.
How factor Xa inhibitors cause anticoagulation
Factor Xa inhibitors are novel anticoagulants. They block the action of
factor Xa which is an important protein in the coagulation cascade that causes
blood to clot. Reducing the action of factor Xa reduces the ability of blood to
clot.
Storage, preparations, and forms available in the US
Preparations
Drugs in this class are available as tablets, capsules, powder for injection,
prefilled syringes, and in vials containing a solution for injection. Some
intravenous anticoagulants (for example, bivalirudin, and heparin) are
administered via an intravenous infusion while receiving medical care in the
hospital.
Storage
Oral anticoagulants are stored at room temperature. Prefilled syringes and
multiple dose vials of low molecular weight heparins, and heparin vials are also
stored at room temperature.