Term
Anticoagulants
Learning Objectives
(4) |
|
Definition
|
•Know the four classes of drugs used as anticoagulants and their mechanisms of action
•Know the major toxicities and contraindications of each class of drug
•Know the major therapeutic applications of each class of drug
•Know how the efficacy of each class of drug is monitored
|
|
|
Term
|
Definition
|
•Coagulation is a highly regulated process involving conversion of soluble fibrinogen (factor I) into insoluble fibrin (factor Ia)
•The conversion fibrinogen to fibrin is regulated by cascades of proteases:
–Thrombin (factor IIa) cleaves fibrinogen to fibrin
–Factor Xa cleaves the inactive zymogen prothrombin (factor II) to thrombin (factor IIa)
–The conversion of factor X to factor Xa is regulated by two distinct clotting cascades:
•The Intrinsic pathway (all factors for this pathway are normally present in the blood)
•The Extrinsic pathway (includes factors not usually present in the blood such as tissue factor (aka- thromboplastin))
|
|
|
Term
Anticoagulants
Clotting Test:
(8) |
|
Definition
- aPTT
- Activated Partial Thromboplastin Time:
- Recalcified plasma plus kaolin plus phospholipids.
- A prolonged aPTT indicates a defect in the intrinsic pathway
- PT
- Prothrombin Time: Recalcified plasma plus thromboplastin.
- A prolonged PT indicates a defect in the extrinsic pathway
- A prolongation of both aPTT and PT suggests a defect in the Common Pathway
-
|
|
|
Term
Two Clotting Tests Used to Monitor
Anticogulant Therapy
(4) |
|
Definition
|
•Activated Partial Thromboplastin Time (aPTT; Intrinsic and Common pathways)
–Used to monitor standard heparin and parenteral direct thrombin inhibitors
•Prothrombin Time (PT; Extrinsic pathway)
–Used to monitor warfarin
|
|
|
Term
Classes of Anticoagulant Drugs
(8) |
|
Definition
|
•The heparinoids: sulfated mucopolysacharides that accelerate the action of endogenous antithrombin III (AT III), including heparin and the low MW heparins
–AT III binds and inactivates several activated clotting factors (thrombin, IXa, Xa, XIa, and XIIa)
–Pentasacharide is a synthetic molecule that binds ATT III and indirectly inactivates factor Xa
•Direct thrombin inhibitors (DTIs): hirudin (parenteral) and dabigatran (oral)
•Direct factor Xa inhibitors: apixaban (oral) and rivaroxaban (oral)
•The vitamin K antagonists (VKAs): warfarin and the coumarin anticoagulants
–These agents inhibit the synthesis of vitamin K-dependent clotting factors
–Also used as rodenticides (e.g., De-Con)
|
|
|
Term
Sites of Action of Anticoagulant Drugs
Inhibited by Heparin
(via AT lll)
(4) |
|
Definition
|
|
Term
Sites of Action of Anticoagulant Drugs
Inhibited by Oral Anticoagulant Drugs
(Warfarin)
(4) |
|
Definition
|
|
Term
Sites of Action of Anticoagulant Drugs
Down-regulated by protein Cact
(3) |
|
Definition
|
|
Term
Anticoagulants
Clotting Enzymes Inhibited by AT lll
(5) |
|
Definition
- Xlla
- Xla
- lXa
- Xa
- Thrombin (Xllla)
|
|
|
Term
Anticoagulants
Heparin
(4) |
|
Definition
|
•Heparin binding to AT III induces a conformational change in AT III that increases its rate of interaction (inhibition) with activated proteases by a factor of >1000
•One heparin molecule can catalyze the activation of many molecules of AT III
•Commercial heparin is extracted from pig intestinal mucosa and bovine lung (rarely used); it is very heterogenenous
•Heparins are administered by continuous or intermittent IV infusion or by subcutaneous injection (slow delivery)
|
|
|
Term
Anticoagulants
Types of Heparin (Heparinoids)
(6) |
|
Definition
|
•Heparin is available as unfractionated (UFH) or fractionated (HMWHs and LMWHs)
•Standard heparin (UFH) markedly inhibits coagulation by inhibiting several activated clotting factors
•Low MW fractions of heparin (LMWHs; enoxaparin, dalteparin, ardeparin, tinzaparin) are more specific for inhibition of factor Xa, though they may also inhibit thrombin
–The LMW heparins are as efficacious as standard heparin, but have increased bioavailability from the subcutaneous site of injection and less frequent dosing requirements (once or twice daily)
–LMWHs are more expensive than standard heparin
–LMWHs are useful in the treatment of deep vein thrombosis (DVT) in the postoperative period, acute venous thromboembolic disease, and acute coronary syndromes
|
|
|
Term
Anticoagulants
Comparison of UFH and LMWHs
(5) |
|
Definition
|
•UFH binds platelets and causes their activation and aggregation, thereby leading to heparin-induced thrombocytopenia; LMWHs have minimal effects on platelets
•UFH binds many plasma proteins and cells; LMWHs have reduced nonspecific binding which increases bioavailability, prolongs plasma half-life, and gives a more predictable anticoagulant response
•UFH inhibits coagulation at many sites; LMWHs are more specific for factor Xa and thrombin, with 1.7 to 4-fold higher specificity towards Xa
•UFH only acts on circulating thrombin, whereas LMWHs also act on clot-bound thrombin
•UFH requires laboratory monitoring of clotting function (aPTT), but LMWHs do not
|
|
|
Term
Anticoagulants
Toxicities of Heparinoids
(7) |
|
Definition
|
•The major adverse effect of heparin is bleeding
–Close monitoring of the activated partial thromboplastin time (aPTT) is required with UFH
–LMWHs have very predictable pharmacokinetics in patients with normal renal function; monitoring (factor Xa inhibitory activity) is not required except in renal insufficiency and pregnancy
•UFH causes transient thrombocytopenia in 25% or more of patients and severe thrombocytopenia in 5%; thrombocytopenia with LMWHs is <2%
–Some patients develop an antibody-mediated thrombo-cytopenia (after 5-10 days) that can cause platelet aggregation and paradoxical thrombosis by platelet-induced thrombin production (thrombosis can lead to death or limb amputation)
–Platelet counts should be performed frequently in all patients
–Thromboembolic disease thought to be heparin-induced should be treated by discontinuing heparin and using lepirudin, argatroban, or danaparoid (but not warfarin since it may exacerbate the prothrombotic state)
|
|
|
Term
Anticoagulants
Otehr Toxicities of Heparinoids
(6) |
|
Definition
|
•Being of animal origin, allergy is possible with heparinoids
–Porcine is less allergenic than bovine
•Hematomas can form if injected intramuscularly rather than subcutaneously
•Osteoporosis is possible with long-term administration of heparinoids (LMWHs cause less osteoporosis than UFH)
•Long-term use is associated with mineralocorticoid deficiency
•Agranulocytosis is also seen in some patients |
|
|
Term
Anticoagulants
Contraindications of Heparinoids
(5) |
|
Definition
|
•Contraindicated in patients:
–who are hypersensitive to the drug
–who are actively bleeding
–who have hemophilia, thrombocytopenia, intrancranial hemorrhage, ulcerative lesions of the GI tract, active TB, infective carditis, threatened abortion, visceral carcinoma, or advanced hepatic or renal disease
–during or after surgery of the brain, spinal cord, or eye, or undergoing lumbar puncture or regional anesthetic block
•Though heparin does not apparently cross the placenta and is not teratogenic, it should only be used in pregnant women when clearly indicated (e.g.- previous thromboembolic events, thrombophilia)
|
|
|
Term
Anticoagulants
Reversal of Heparinoid Action
(6) |
|
Definition
|
•Excessive anticoagulation is treated by discontinuation of drug
•If bleeding occurs, the effects of UFH can be neutralized by administration of protamine sulfate, a polycationic peptide
–Excess protamine has an anticoagulant effect
–Neutralization of UFH is incomplete
•Enoxaparin can also be neutralized somewhat by protamine, though LMWHs are not well reversed by protamine
•Danaparoid can be removed by plasmapheresis
|
|
|
Term
Anticoagulants
Fondaparinux (pentasaccharide, Arixtra)
(11) |
|
Definition
|
•A homogeneous synthetic pentasaccharide (MW 1728) developed using knowledge of the structural determinants of heparin required for high affinity binding to AT III; it does not inhibit thrombin
•It is classified as an indirect factor Xa inhibitor
•Compared to UFH and LMWH:
–It has a higher affinity for AT III
–It specifically enhances the rate of factor Xa inactivation by AT III with no effect on thrombin inactivation
–It can inhibit platelet-bound factor Xa
–It does not cross-react with the heparin-induced antibody
–It appears to be more effective than LMWHs in patients undergoing knee or hip surgeries (its primary indication)
–It may also be useful for treating PE, DVT, ACS
•It has complete bioavailability after subcutaneous injection and a half-life of 17-21 hours (cleared intact by the kidney; avoid in patients with renal failure)
•Unlike the heparinoids, its actions cannot be reversed
|
|
|
Term
Anticoagulants
Direct Thrombin Inhibitors-Parenteral
Hirudin
(9) |
|
Definition
|
•Hirudin (lepirudin) is the prototype DTI
–Lepirudin (Refludan) is recombinant hirudin
–Lepirudin binds thrombin specifically and tightly
•Its action is independent of AT III so it can inactivate fibrin-bound thrombin in clots
–Lepirudin has little effect on platelets or bleeding time
•Dosing is monitored by the aPTT
–Approved for use in patients with heparin-induced thrombocytopenia
–Administered parenterally and has a short half-life
--Long-term infusions can lead to antibodies directed against thrombin-lepirudin complexes; this can slow clearance by the kidneys (resulting in an enhanced anticoagulant effect) |
|
|
Term
Anticoagulants
Direct Thrombin Inhibitors-Parenteral
Bivalirudin
(8) |
|
Definition
|
•Bivalirudin (Angiomax) is a bivalent semi-synthetic 20-residue peptide
–Consists of a D-Phe-Pro-Arg-Pro active-site directed sequence, a (Gly)4 linker, and a 12-amino acid peptide analog of the C-terminus of hirudin which binds exosite 1 in thrombin (thus its binding to thrombin is bivalent)
–This agent differs from hirudin in having a more transient inhibition of thrombin since cleavage of the Arg-Pro bond by thrombin weakens its affinity
–Approved for use in patients undergoing coronary angioplasty (PCI), for acute MI with streptokinase, and for DVT prophylaxis for hip and knee surgery
•Desirudin (Iprivask) is a bivalent recombinant analog of hirudin
–Approved for DVT prophylaxis for total hip replacement and is more effective than heparinoids
•Argatroban (Acova) is a synthetic N2-substituted derivative of arginine that binds the active site of thrombin non-covalently (reversibly)
–It is approved for use in patients with heparin-induced thrombocytopenia
|
|
|
Term
Anticoagulants
Direct Thrombin Inhibitors - Oral
(4) |
|
Definition
|
•Dabigatran (Pradax) was approved in 2010 for use in patients with atrial fibrillation to prevent ischemic stroke and venous thrombolic events (VTEs)
•Dabigatran is well-absorbed, has faster onset of action than warfarin, has no known pharmacokinetic drug interactions, can be given as a fixed dose, and does not require routine coagulation monitoring
•Clinical trials (RE-LY) with >18,000 patients show dabigatran is better than warfarin at preventing ischemic stroke and VTEs, and is equivalent to warfarin in terms of bleeding risk
•Drug costs are higher but may be as cost-effective as warfarin due to reduced overall costs (no INR monitoring and reduced thromboembolic events)
|
|
|
Term
Anticoagulants
Warfarin and Coumadin
(4) |
|
Definition
|
•Commonly referred to as vitamin K antagonists (VKAs)
•Warfarin is the most widely used VKA in the US
•VKAs act to inhibit coagulation by blocking the g-carboxylation of Glu residues on factors II (prothrombin), VII, IX, and X
–Without g-carboxylation, these factors are inactive
|
|
|
Term
Anticoagulants
Mechanism of Warfarin Action
(4) |
|
Definition
|
•Warfarin prevents reductive activation of vitamin K which is required for g-carboxylation of several clotting factors, as well as anticoagulant Proteins C and S
•Blocking g-carboxylglutamate synthesis results in clotting factors that are biologically inactive
•The molecular target of warfarin is Vitamin-K oxidoreductase complex 1 (VKORC1)
• SNPs in VKORC1 account for 20-30% of warfarin dose variability
|
|
|
Term
Anticoagulants
Warfarin Onset of Action |
|
Definition
|
•There is an 8-12 hour delay in onset of action which is dependent upon the rates of degradation of the four vitamin K-dependent clotting factors
–The half-lives of the clotting factors ranges from 6 hours for factor VII, to 60 hours for thrombin
–At low doses of warfarin, synthesis of clotting factors is only partially inhibited and the onset of action is dose-dependent
–At high doses of warfarin (inadvisable), where synthesis is fully blocked, the onset of action is determined by clotting factor half-life
•There is a 1-3 day delay in maximum hypo-prothrombinemia following peak drug concentration
•Therapy should be initiated with low doses over 1-2 weeks and monitored by prothrombin time (preferably using INR)
•There can be an initial prothrombotic effect due inhibition of the anticoagulant, Protein C, which has a short half-life (6 hrs)
|
|
|
Term
Anticoagulants
Monittoring Warfarin Efficacy
(5) |
|
Definition
|
•Warfarin efficacy is measured using the prothrombin time (PT) clotting assay
•The efficacy of warfarin should be tested at the beginning of therapy (daily) until appropriate dosing is obtained and PT is stable for 2 days, then periodically (1-4 weeks) after that
•In order to ensure consistency among clinical laboratories, the international normalized ratio (INR) is the preferred system for reporting PT
–The INR is the prothrombin time normalized to a control assay performed with an international reference thromboplastin (tissue factor)
•Use of the INR system has resulted in the use of lower doses of warfarin, less bleeding episodes, and the same efficacy as higher doses of warfarin
|
|
|
Term
Anticoagulants
INR Equation
(10) |
|
Definition
- INR = [(Pt's PT in secs)/(Mean normal PT in secs)]ISI
- INR = International Normalized Ratio
- ISI = International Sensitivity Index
- PT = Prothrombin Time
- The INR is calculated by the formula shown on this slide.
- The ISI is the International Sensitivity Index.
- Each thromboplastin is assigned an ISI which reflects the sensitivity of the thromboplastin to Warfarin-mediated reduction of the Vitamin K dependent clotting factors.
- By convention, the ISI of the reference thromboplastin is 1.0.
- The higher the ISI, the less sensitive the thromboplastin is to Warfarin-mediated reduction of the Vitamin K dependent clotting factors.
- The next two slides provide an example of how the ISI (sensitivity) of the thromboplastin influences the PT ratio (PTR) and how the resulting variability is corrected by expressing the results as an INR.
|
|
|
Term
Anticoagulants
Factors that can Alter Warfarin Efficacy
(12) |
|
Definition
|
•There can be a nearly 100-fold inter-individual difference in optimal warfarin dosing
–Age, gender, weight, diet, co-morbidity, ethnicity, and concomitant drug use all contribute to dosing variability
•Genetic polymorphisms in VKORC1 and CYP2C9 can account for upwards of 40% of dose variability
•Changes in diet (weight loss diets, traveling, or hospitalization) can change vitamin K intake
•Changes in hormonal status
–Hypothyroidism can reduce efficacy
–Hyperthyroidism can increase efficacy
•Changes in liver or kidney function
–Synthesis and excretion of clotting factors
–Altered drug metabolism
•Changes in concomitant drugs
–A large number of drugs interact with warfarin and can either increase or reduce its anticoagulant effects
|
|
|
Term
Anticoagulants
Warfarin Drug Interactions
(10) |
|
Definition
|
•Warfarin probably has more drug interactions than any other agent
•Warfarin interactions can either increase anticoagulant effect (serious because the risk of bleeding increases) or decrease it (increasing the risk of thrombosis)
•Pharmacokinetic interactions
–Enzyme induction
–Enzyme inhibition
–Reduced plasma protein binding
•Pharmacodynamic interactions
–Synergism (impaired hemostasis; reduced clotting factor synthesis as in liver disease; increased urinary excretion of clotting factors with diuretics)
–Competitive antagonism (vitamin K)
–Altered physiological control loop for vitamin K (hereditary resistance to oral anticoagulants)
|
|
|
Term
Anticoagulants
Warfarin Toxicity
(3) |
|
Definition
|
•Warfarin crosses the placenta and can cause hemorrhagic disorders in the fetus as well birth defects since bone formation requires g-carboxylglutamate synthesis
•Cutaneous necrosis with reduced activity of Protein C sometimes occurs during the first weeks of therapy
•Hemorrhagic infarction due to venous thrombosis occurs more rarely, and is probably due to warfarin inhibition of Protein C synthesis
|
|
|
Term
Anticoagulants
Relative Contraindications to Warfarin
(4) |
|
Definition
|
•Pregnancy
•Situations where the risk of hemorrhage is greater than the potential clinical benefits of therapy
–Uncontrolled alcohol/drug abuse
–Unsupervised dementia/psychosis
|
|
|
Term
Anticoagulants
Relative Contraindications to Warfarin
Notes page
(5) |
|
Definition
|
- The relative contraindications for warfarin are listed on this slide.
- Warfarin crosses the placenta and is teratogenic in the first trimester, producing warfarin embryopathy in about 5% of exposed neonates.
- It is also fetopathic when used after the first trimester in an unknown (but much smaller) percentage of fetuses.
- Warfarin is contraindicated (relative or absolute) in patients with an increased risk of serious bleeding.
- The indication for warfarin should be reviewed carefully in patients with relative contraindications.
|
|
|
Term
Anticoagulants
Signs of Warfarin Overdosage
(7) |
|
Definition
|
•Any unusual bleeding:
–Blood in stools or urine
–Excessive menstrual bleeding
–Bruising
–Excessive nose bleeds/bleeding gums
–Persistent oozing from superficial injuries
–Bleeding from tumor, ulcer, or other lesion
|
|
|
Term
Anticoagulants
Signs of Warfarin Overdosage
Notes Page
(4) |
|
Definition
- The signs of warfarin overdosage are listed on this slide.
- Hemorrhagic complications from warfarin therapy are more likely to occur with excessive degrees of anticoagulation, but even with an INR in the therapeutic range, bleeding can occur.
- Because of the likelihood of finding an underlying lesion in an individual who has gastrointestinal bleeding or significant genito-urinary bleeding in the face of therapeutic levels of anticoagulation, one is advised to consider and evaluate for underlying abnormalities predisposing to the bleeding.
- The return on such evaluations in the face of an excessive degree of anticoagulation diminishes, and one must use judgement whether or not to pursue an evaluation.
|
|
|
Term
Anticoagulants
Reversal of Warfarin Action
(9) |
|
Definition
|
•Modest excess of anticoagulant activity can be corrected by adjusting dose of anticoagulant drug
•Excessive anticoagulant effect can be reversed by:
–Stopping the drug
–Administering large doses of vitamin K1 (phytonadione)
–Administering fresh-frozen plasma or factor IX concentrates (Konyne 80, Proplex T) that contain large amounts of prothrombin complex
•Serious bleeding requires:
–High doses of vitamin K1 administered IV
–Factor IX concentrates
–Sometimes whole blood transfusions
|
|
|
Term
Anticoagulants
Warfarin Indications
(6) |
|
Definition
|
•Prevention of:
–Venous thromboembolism
–Systemic embolism associated with AF and prosthetic heart valves
–Acute MI in patients with peripheral arterial disease or men otherwise at high risk
–Prevention of stroke, recurrent infarction, or death in patients with AMI
–Systemic embolism in high-risk patients with mitral stenosis and in patients with presumed systemic embolism
|
|
|
Term
Warfarin Current Indications/Intensity
Notes page
|
|
Definition
- For most indications a therapeutic range of 2.0 to 3.0 is recommended.
- A higher INR range of 2.5 to 3.5 is recommended for parents with mechanical prosthetic valves and post myocardial infarction and for some patients with antiphospholipid syndrome and a history of thrombosis.
|
|
|
Term
Warfarin: Dosing & Monitoring
(7) |
|
Definition
|
•Start low (not with a loading dose)
–Initiate therapy with average maintenance dose (5 mg daily; Elderly, frail, liver disease, malnourished: 2 mg/day)
–If rapid anticoagulation is required, use concurrent heparin for >/= 4 days until INR is in therapeutic range for 2 days
–Check INR daily until therapeutic range has been reached and sustained for 2 consecutive days; titrate dosage to obtain desired INR
–Once the INR has become stable, INR testing can be reduced to intervals as long as 4 weeks
•If dose adjustments are necessary, resume frequent INR testing until stable
•Point-of-care PT testing is now available and is very useful in keeping INR at desired level
|
|
|
Term
Warfarin: Dosing & Monitoring
Notes page
(4) |
|
Definition
- This slide provides guidelines for safe and effective warfarin use.
- The dose of warfarin should be monitored daily until the INR is in the therapeutic range and then less frequently when a stable dose-response relationship is achieved.
- Regardless of the degree of stability in warfarin dosing and INR value in the hospital, it is important to monitor the INR frequently post hospital discharge (i.e., at least 1–3 days after discharge) and to spread out the interval of monitoring thereafter depending on INR response.
- Monitoring is necessary in all patients, but can be reduced to four weekly intervals in the low risk (for bleeding) patient who shows a stable dose-response.
|
|
|
Term
Conversion from Heparin to Warfarin
(5) |
|
Definition
|
•May begin warfarin concomitantly with heparin therapy to achieve rapid anticoagulation effect
•Monitor INR daily until stable for 2 days
•Heparin should be continued for a minimum of four days
–Time to peak antithrombotic effect of warfarin is delayed 96 hours (despite INR)
•When INR reaches desired therapeutic range for 2 days, discontinue heparin (after a minimum of four days)
|
|
|
Term
Conversion from Heparin to Warfarin
Notes page
(3) |
|
Definition
- When short-term heparin followed by long-term warfarin are used, both anticoagulants can be started simultaneously.
- Heparin should be continued for a minimum of four days because the peak antithrombotic effect of warfarin is delayed for about 96 hours, independently of the INR, until Factor II (prothrombin is reduced).
- Heparin can be discontinued after a minimum of four days when the INR reaches the therapeutic range.
|
|
|
Term
Recent Oral Anticoagulants -
Possible Replacements For Warfarin
(4) |
|
Definition
|
•The FDA has recently approved the use of new orally active small molecule direct-acting inhibitors of thrombin and factor Xa for many of the primary indications of warfarin therapy
–Dabigatran (Pradaxa) is a direct-acting thrombin inhibitor
–Rivaroxaban(Xarelto) is a direct-acting factor Xa inhibitor
•These agents have rapid onset of action (1-4 hours), do not require bridge therapy with heparinoids, and do not require laboratory anticoagulant monitoring
|
|
|
Term
Anticoagulants
Dabigatran Etexilate (Pradaxa)
(7) |
|
Definition
|
•First orally active direct-acting thrombin inhibitor
•Dabigatranexilate is a prodrug that must be metabolized to the active form, dabigatran
•Clinical trials indicate it is as efficacious as warfarin, with similar or reduced risk of major bleeding
•Rapid onset of action (1-2 hours), 3-7% bioavailability, 80% renal excretion, twice-daily dosing
•No known pharmacogenetic interactions; few interactions with food
•Does not require laboratory anticoagulant monitoring
•No antidote if toxicity (i.e., excess anti-coagulation)
•
|
|
|
Term
Anticoagulants
Rivaroxaban (Xarelto)
(7) |
|
Definition
|
•First approved direct-acting factor Xa inhibitor
–Approved July 2011 for use in preventing DVTs in patients with hip or knee replacements (superior to enoxaparin)
–Approved November 2011 to prevent stroke and systemic embolism in non-valvular atrial fibrillation (lower risk of intracranial and fatal bleeding than warfarin)
•Rapid onset of action (2-4 hours), 80% oral bioavailability (with food), 70% hepatic(CYP3A4/5), 30% renal excretion, once-daily dosing
•No known pharmacogenetic interactions; few interactions with food
•Does not require laboratory anticoagulant monitoring
•No antidote if toxicity (i.e., excess anti-coagulation)
|
|
|
Term
Anticoagulants
Warfarin or Newer Oral Anticoagulants?
(9)
|
|
Definition
|
•Cost of drug (newer agents are expensive)
•Laboratory monitoring (required for warfarin but anticoagulant monitoring protocols would be useful for the newer agents)
•Pharmacogenetic interactions (warfarin)
•Drug-drug and drug-food interactions (warfarin)
•Adherence (newer agents have short half-lives and need to be taken daily)
•Efficacy (newer agents may be comparable or more efficacious than warfarin, but data comparing newer agents to one another is lacking)
•Serious bleeding events (may be less risk with newer agents)
•Unknown adverse effects (newer agents lack a track record in real world settings)
•What about renal disease, trauma, surgery?
|
|
|
Term
Anticoagulants
Warfarin or Newer Oral Anticoagulants?
Joint committee |
|
Definition
| A joint committee of the American College of Cardiology and American Heart Association has recently recommended that patients with atrial fibrillation who have been stable and well controlled on warfarin should remain on warfarin rather being switched to dabigatran. |
|
|
Term
Anticoagulants
Key Concepts
(4) |
|
Definition
|
•Anticoagulants are used to prevent the formation of fibrin clots
•Anticoagulant drugs either reduce the activation of thrombin (directly or indirectly), or inhibit thrombin (directly or indirectly)
•Parenteral anticoagulants are used acutely (days to weeks), whereas oral anticoagulants are used chronically (often indefinitely)
•Bleeding is the most common and serious toxicity of all anticoagulants
|
|
|
