anticoagulants ppt

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					1
   Anticoagulants interfere either directly
    or indirectly with the clotting cascade.




                                        2
   Directly acting >>>> low/high molecular
    weight HEPARIN



   Indirectly acting >>>>> coumarins
    (warfarin and acenocoumarol)



                                        3
   Heparin is a heterogeneous mixture of sulfated (anionic)
    mucopolysaccharides named because of its initial discovery
    in high concentrations in the liver.



   It is prepared from porcine intestinal mucosa and bovine
    lung.




                                                        4
   It acts indirectly to facilitate endogenous anticoagulants,
    specifically antithrombin III and heparin cofactor II.



   These molecules form stable complexes with (and thus
    inactivate) clotting factors, especially thrombin.




                                                           5
   Heparin is released in its active form after inactivation of
    the clotting factor and thus can interact with other
    molecules.

   The effect is greater with low concentrations of heparin.

   Heparin is also antithrombotic due to binding to endothelial
    cell walls, thus impairing platelet aggregation and
    adhesion.




                                                            6
   Heparin can be given IV (either intermittently or as a
    constant infusion) or SC.

   Deep SC or intrafat injection prolongs persistence of
    therapeutic concentrations.

   Large hematomas can develop after deep IM injection.




                                                            7
   High-dose heparin therapy ( 150-250 U/kg, tid) has been
    recommended for established thromboembolism.



   Lower dosages (75 U/kg, tid) are indicated in the
    management of DIC.

   Blood coagulation times (eg, activated partial
    thromboplastin time) should be monitored during therapy.




                                                        8
    >>>>>>prevention or treatment of
    venous or pulmonary embolism



   >>>>>> and embolization associated
    with atrial fibrillation.


                                   9
   It is also used as an anticoagulant for diagnostic use and
    blood transfusions.

   Heparin is used in conjunction with blood and/or plasma
    for the treatment of disseminated intravascular
    coagulopathy (DIC) and other hypercoagulable conditions.

   Heparin has also been used to clear hyperlipidemia




                                                         10
   Heparin is available as a sodium or calcium salt.



   Absorption and distribution of heparin are limited by the
    large size and polarity of the molecule.



   Oral absorption is poor; hence, it is a parenteral
    anticoagulant.




                                                         11
   Although anticoagulant activity is first
    order, half-life of the drug is dose-
    dependent, steady-state
    concentrations are difficult to achieve,
    and pharmacokinetics vary among
    individuals.




                                       12
   Heparin is metabolized by heparinase in the liver and by
    reticuloendothelial cells.

   Metabolites of heparinase activity are excreted in the
    urine.




   The half-life is prolonged in renal or hepatic failure.




                                                              13
   Heparin can be given IV (either intermittently or as a constant
    infusion) or SC.



   Deep SC or intrafat injection prolongs persistence of therapeutic
    concentrations.



   Large hematomas can develop after deep IM injection.




                                                               14
   Side effects and toxicities of heparin are limited to potential
    hemorrhage, and because heparin is a foreign protein,
    >>>>>>>possible allergic reactions may be experience by
    patients




   Heparin is contraindicated in bleeding animals and in DIC unless
    replacement blood or plasma therapy is also given




                                                                 15
   Natural heparin consists of molecular
    chains of varying lengths, or molecular
    weights.

   Chains of molecular weight from 5000 to
    over 40,000 Daltons, making up
    polydisperse pharmaceutical-grade
    heparin.

                                         16
   LMWHs are defined as heparin salts
    having an average molecular weight of
    less than 8000 Da and for which at least
    60% of all chains have a molecular
    weight less than 8000 Da.

   These are obtained by various methods
    of fractionation or depolymerisation of
    polymeric heparin.
                                        17
 The effects of LMWHs cannot be
  measured using the partial
  thromboplastin time (PTT) or activated
  clotting time (ACT) tests.
 Rather, LMWH therapy is monitored by
  the anti-factor Xa assay, measuring anti-
  factor Xa activity.



                                       18
   The antifactor Xa activity of heparin is
    relatively unaffected by the molecular
    weight of heparin and is therefore less
    influenced by the effect of
    potent heparin antagonists which can
    be released from platelets.




                                          19
   The methodology of an anti-factor Xa
    assay is that patient plasma is added to
    a known amount of excess factor Xa
    and excess antithrombin.

   If heparin or LMWH is present in the
    patient plasma, it will bind to
    antithrombin and form a complex with
    factor Xa, inhibit it.
                                        20
   The amount of residual factor Xa is
    inversely proportional to the amount of
    heparin/LMWH in the plasma.




                                        21
   The amount of residual factor Xa is
    detected by adding a chromogenic
    substrate that mimics the natural
    substrate of factor Xa, making residual
    factor Xa cleave it, releasing a colored
    compound that can be detected by
    a spectrophotometer.



                                         22
   Antithrombin deficiencies in the patient
    do not affect the assay, because excess
    amounts of antithrombin is provided in
    the reaction.




                                        23
   Results are given in anticoagulant
    concentration in units/mL of antifactor
    Xa, such that high values indicate high
    levels of anticoagulation and low values
    indicate low levels of anticoagulation.




                                        24
   LMWHs have a potency of greater than
    70 units/mg of anti-factor Xa activity and
    a ratio of anti-factor Xa activity anti-
    thrombin activity of >1.5




                                         25
 Oxidative depolymerisation with
  hydrogen peroxide. Used in the
  manufacture of ardeparin (Normiflo)
 Deaminative cleavage with isoamyl
  nitrite. Used in the manufacture
  of certoparin (Sandoparin)




                                        26
   Alkaline beta-eliminative cleavage of
    the benzyl ester of heparin. Used in the
    manufacture of enoxaparin(Lovenox
    and Clexane)




                                         27
 Oxidative depolymerisation with
  Cu2+ and hydrogen peroxide. Used in the
  manufacture ofparnaparin (Fluxum)
 Beta-eliminative cleavage by the
  heparinase enzyme. Used in the
  manufacture of tinzaparin(Innohep and
  Logiparin)



                                    28
   Deaminative cleavage with nitrous acid.
    Used in the manufacture
    of dalteparin (Fragmin), reviparin(Clivarin
    ) and nadroparin (Fraxiparin)




                                          29
   Comparisons between LMWHs prepared
    by similar processes vary. For example, a
    comparison of Dalteparin and
    Nadroparin suggests they are more
    similar than products produced by
    different processes.





                                         30
   However, comparison of enoxaparin
    and tinzaparin shows they are very
    different from each other with respect to
    chemical, physical, and biological
    properties.




                                         31
   As might be expected, products
    prepared by distinctly-different
    processes are dissimilar in physical,
    chemical, and biological properties.




                                            32
 Average molecular weight: heparin is
  about 15 kDa and LMWH is about 4.5 kDa.
 Once-daily dosing by subcutaneous
  injection, rather than a continuous infusion
  of unfractionated heparin.




                                        33
   No need for monitoring of
    the APTT coagulation parameter.



   Smaller risk of osteoporosis in long-term
    use.



                                           34
   Smaller risk of heparin-induced
    thrombocytopenia, a feared side-effect
    of heparin.




                                      35
   The anticoagulant effects of heparin are
    typically reversible with protamine
    sulfate, while protamine's effect on
    LMWH is limited.



   Has less of an effect on thrombin possibly
    a smaller risk of bleeding

                                         36
   Because it can be given subcutaneously
    and does not require APTT monitoring,
    LMWH permits outpatient treatment of
    conditions such as deep vein
    thrombosis or pulmonary embolism that
    previously mandated inpatient
    hospitalization for unfractionated
    heparin administration.


                                      37
   Because LMWH has more
    predictable pharmacokinetics and
    anticoagulant effect, LMWH is
    recommended over unfractionated
    heparin for patients with massive
    pulmonary embolism, and for initial
    treatment of deep vein thrombosis.



                                          38
   Prophylactic treatment of hospitalized
    medical patients with LMWH and similar
    anticoagulants results in a 53% reduction
    of risk for symptomatic deep vein
    thrombosis.




                                         39
 The use of LMWH needs to be monitored
  closely in patients at extremes of weight
  or in-patients with renal dysfunction.
 An anti-factor Xa activity may be useful
  for monitoring anticoagulation.




                                       40
   Given its renal clearance, LMWH may
    not be feasible in patients that
    have end-stage renal disease




                                      41
   In patients with malignancy and acute
    venous thromboembolism, dalteparin
    was more effective than coumarin in
    reducing the risk of recurrent embolic
    events.




                                       42
   Use of LMWH in cancer patients for at
    least the first 3 to 6 months of long-term
    treatment is recommended in numerous
    guidelines and is now regarded as a
    standard of care.




                                          43
44
45
   Warfarin (also known under the brand
    names
    Coumadin, Jantoven, Marevan, Lawarin,
    and Waran) is an anticoagulant.




                                     46
   Warfarin was found to be effective and
    relatively safe
    for preventing thrombosis and embolism(
    abnormal formation and migration of
    blood clots) in many disorders.




                                       47
 Despite its effectiveness, treatment with
  warfarin has several shortcomings.
 Many commonly used
  medicationsinteract with warfarin, as do
  some foods, and its activity has to be
  monitored by frequent blood testing for
  the international normalized ratio (INR) to
  ensure an adequate yet safe dose is
  taken
                                        48
 Warfarin is a synthetic derivative
  of dicoumarol, a 4-hydroxycoumarin-
  derived mycotoxin anticoagulant found in
  spoiled clover-based animal feeds.
 Dicoumarol, in turn, is derived
  from coumarin, a chemical found naturally
  in many plants (not to be confused
  with Coumadin, a brand name for
  warfarin).
 Coumarin itself has no effect on clotting, or
  upon the action of warfarin.
                                           49
   Warfarin and related 4-
    hydroxycoumarin-containing molecules
    decrease blood coagulation by
    inhibiting vitamin K epoxide reductase,
    an enzyme that recycles oxidized
    vitamin K to its reduced form after it has
    participated in the carboxylation of
    several blood coagulation proteins,
    mainly prothrombin and factor VII.
                                          50
   For this reason, drugs in this class are also
    referred to as vitamin K antagonists.




                                            51
   Warfarin inhibits the vitamin K-
    dependent synthesis of biologically
    active forms of the calcium-
    dependent clotting factors II, VII, IX and
    X, as well as the regulatory
    factors protein C, protein S, and protein
    Z.



                                          52
   The precursors of these factors
    require carboxylation of their glutamic
    acid residues to allow the coagulation
    factors to bind to phospholipid surfaces
    inside blood vessels, on the
    vascular endothelium.




                                         53
   The enzyme that carries out the
    carboxylation of glutamic acid
    is gamma-glutamyl carboxylase.

   The carboxylation reaction will proceed
    only if the carboxylase enzyme is able to
    convert a reduced form of vitamin K
    (vitamin K hydroquinone) to vitamin K
    epoxide at the same time
                                         54
   The vitamin K epoxide is in turn recycled back
    to vitamin K and vitamin K hydroquinone by
    another enzyme, the vitamin K epoxide
    reductase (VKOR).


   Warfarin inhibits epoxide
    reductase (specifically the VKORC1 subunit),
    thereby diminishing available vitamin K and
    vitamin K hydroquinone in the tissues, which
    inhibits the carboxylation activity of the
    glutamyl carboxylase.

                                              55
   When this occurs, the coagulation
    factors are no longer carboxylated at
    certain glutamic acid residues, and are
    incapable of binding to the endothelial
    surface of blood vessels, and are thus
    biologically inactive.




                                        56
   As the body's stores of previously-produced
    active factors degrade (over several days)
    and are replaced by inactive factors, the
    anticoagulation effect becomes apparent.
    The coagulation factors are produced, but
    have decreased functionality due to
    undercarboxylation; they are collectively
    referred to as PIVKAs (proteins induced [by]
    vitamin K absence/antagonism), and
    individual coagulation factors as PIVKA-
    number (e.g. PIVKA-II). The end result of
    warfarin use, therefore, is to diminish blood
    clotting in the patient.
                                            57
   When warfarin is newly started, it may promote clot
    formation temporarily. This is because the level
    ofprotein C and protein S are also dependent on
    vitamin K activity. Warfarin causes decline in protein
    C levels in first 36 hours. In addition, reduced levels of
    protein S lead to a reduction in activity of protein
    C(for which it is the co-factor) and therefore reduced
    degradation of factor Va and factor VIIIa. Although
    loading doses of warfarin over 5 mg also produce a
    precipitous decline in factor VII, resulting in an initial
    prolongation of the INR, full antithrombotic effect
    does not take place until significant reduction in
    factor II occurs days later



                                                       58
   The hemostasis system becomes
    temporarily biased towards thrombus
    formation, leading to a prothrombotic
    state. Thus, when warfarin is loaded rapidly
    at greater than 5 mg per day, it is beneficial
    to co-administer heparin, an anticoagulant
    that acts upon antithrombin and helps
    reduce the risk of thrombosis, with warfarin
    therapy for four to five days, in order to
    have the benefit of anticoagulation from
    heparin until the full effect of warfarin has
    been achieved

                                             59
   Warfarin is prescribed to people with an
    increased tendency for thrombosis or as
    secondary prophylaxis (prevention of
    further episodes) in those individuals that
    have already formed a blood clot
    (thrombus). Warfarin treatment can help
    prevent formation of future blood clots and
    help reduce the risk of embolism (migration
    of a thrombus to a spot where it blocks
    blood supply to a vital organ).
                                          60
   The type of anticoagulation (clot formation inhibition) for
    which warfarin is best suited, is that in areas of slowly-
    running blood, such as in veins and the pooled blood
    behind artificial and natural valves, and pooled in
    disfunctional cardiac artria. Thus, common clinical
    indications for warfarin use are atrial fibrillation, the
    presence of artificial heart valves, deep venous
    thrombosis, and pulmonary embolism(where the
    embolized clots first form in veins). Warfarin is also used
    in antiphospholipid syndrome. It has been used
    occasionally after heart attacks (myocardial infarction),
    but is far less effective at preventing new thromboses in
    coronary arteries. Prevention of clotting in arteries is usually
    undertaken with antiplatelet drugs, which act by a
    different mechanism from warfarin (which normally has no
    effect on platelet function).

                                                             61
   Dosing of warfarin is complicated by the fact that it is
    known to interact with many commonly-used
    medications and even with chemicals that may be
    present in certain foods.[1] These interactions may
    enhance or reduce warfarin's anticoagulation effect.
    In order to optimize the therapeutic effect without
    risking dangerous side effects such as bleeding, close
    monitoring of the degree of anticoagulation is
    required by blood testing (INR). During the initial
    stage of treatment, checking may be required daily;
    intervals between tests can be lengthened if the
    patient manages stable therapeutic INR levels on an
    unchanged warfarin dose.



                                                      62
   When initiating warfarin therapy
    ("warfarinization"), the doctor will decide
    how strong the anticoagulant therapy
    needs to be. The target INR level will vary
    from case to case depending on the
    clinical indicators, but tends to be 2–3 in
    most conditions. In particular, target INR
    may be 2.5–3.5 (or even 3.0–4.5) in
    patients with one or more mechanical
    heart valves.
                                          63
   In some countries, other coumarins are used instead
    of warfarin, such
    as acenocoumarol andphenprocoumon. These have
    a shorter (acenocoumarol) or longer
    (phenprocoumon) half-life, and are not completely
    interchangeable with warfarin. The oral
    anticoagulant ximelagatran (trade name Exanta)
    was expected to replace warfarin to a large degree
    when introduced; however, reports
    of hepatotoxicity(liver damage) prompted its
    manufacturer to withdraw it from further
    development. Other drugs offering the efficacy of
    warfarin without a need for monitoring, such
    as dabigatran and rivaroxaban, are under
    development.

                                                 64
   Pregnancy::::::Warfarin is contraindicated in
    pregnancy, as it passes through the placental barrier
    and may cause bleeding in the fetus; warfarin use
    during pregnancy is commonly associated
    with spontaneous abortion, stillbirth, neonatal death,
    and preterm birth. Coumarins (such as warfarin) are
    alsoteratogens, that is, they cause birth defects; the
    incidence of birth defects in infants exposed to
    warfarin in utero appears to be around 5%, although
    higher figures (up to 30%) have been reported in
    some studies.[15] Depending on when exposure
    occurs during pregnancy, two distinct combinations
    of congenital abnormalities can arise.



                                                    65
   When warfarin (or another coumarin derivative) is given
    during the first trimester—particularly between the sixth
    and ninth weeks of pregnancy—a constellation of birth
    defects known variously as fetal warfarin
    syndrome (FWS), warfarin embryopathy, or coumarin
    embryopathy can occur. FWS is characterized mainly
    by skeletal abnormalities, which include nasal hypoplasia,
    a depressed or narrowed nasal bridge, scoliosis,
    and calcifications in the vertebral column, femur,
    and heel bonewhich show a peculiar stippled
    appearance on X-rays. Limb abnormalities, such
    as brachydactyly(unusually short fingers and toes) or
    underdeveloped extremities, can also occur. Common
    non-skeletal features of FWS include low birth
    weight and developmental disabilities


                                                        66
   Warfarin administration in the second and third trimesters is much
    less commonly associated with birth defects, and when they do
    occur, are considerably different from fetal warfarin syndrome.
    The most common congenital abnormalities associated with
    warfarin use in late pregnancy are central nervous
    system disorders, including spasticity and seizures, and eye
    defects. Because of such later pregnancy birth defects,
    anticoagulation with warfarin poses a problem in pregnant
    women requiring warfarin for vital indications, such
    as stroke prevention in those with artificial heart valves. Usually,
    warfarin is avoided in the first trimester, and a low molecular
    weight heparin such asenoxaparin is substituted. With heparin,
    risk of maternal hemorrhage and other complications is still
    increased, but heparins do not cross the placental barrier and
    therefore do not cause birth defects.Various solutions exist for
    the time around delivery.



                                                                67
   Hemorrhage
   The only common side effect of warfarin
    is hemorrhage (bleeding). The risk of severe bleeding is
    small but definite (a median annual rate of 0.9 to 2.7% has
    been reported[) and any benefit needs to outweigh this
    risk when warfarin is considered as a therapeutic measure.
    Risk of bleeding is augmented if the INR is out of range
    (due to accidental or deliberate overdose or due to
    interactions), and may cause hemoptysis (coughing up
    blood), excessive bruising, bleeding from nose or gums, or
    blood in urine or stool.
   The risks of bleeding is increased when warfarin is
    combined with antiplatelet drugs such
    asclopidogrel, aspirin, or other nonsteroidal anti-
    inflammatory drugs.The risk may also be increased in
    elderly patients[18] and in patients on hemodialysis.

                                                        68
   Warfarin necrosis
   A rare but serious complication resulting from treatment
    with warfarin is warfarin necrosis, which occurs more
    frequently shortly after commencing treatment in patients
    with a deficiency of protein C. Protein C is an innate
    anticoagulant that, like the procoagulant factors that
    warfarin inhibits, requires vitamin K-dependent
    carboxylation for its activity. Since warfarin initially
    decreases protein C levels faster than the coagulation
    factors, it can paradoxically increase the blood's
    tendency to coagulate when treatment is first begun
    (many patients when starting on warfarin are
    given heparin in parallel to combat this), leading to
    massive thrombosis with skin necrosis and gangrene of
    limbs. Its natural counterpart, purpura fulminans, occurs in
    children who are homozygous for certain protein C
    mutations.
                                                          69
   Osteoporosis
   After initial reports that warfarin could reduce bone
    mineral density, several studies have demonstrated a
    link between warfarin use and osteoporosis-
    related fracture. A 1999 study in 572 women taking
    warfarin for deep venous thrombosis, risk of vertebral
    fracture and rib fracture was increased; other
    fracture types did not occur more commonly. A 2002
    study looking at a randomly selected selection of
    1523 patients with osteoporotic fracture found no
    increased exposure to anticoagulants compared to
    controls, and neither did stratification of the duration
    of anticoagulation reveal a trend towards fracture.


                                                      70
   A 2006 retrospective study of 14,564
    Medicare recipients showed that warfarin
    use for more than one year was linked with
    a 60% increased risk of osteoporosis-related
    fracture in men; there was no association in
    women. The mechanism was thought to be
    a combination of reduced intake of vitamin
    K, which is necessary for bone health, and
    inhibition by warfarin of vitamin K-mediated
    carboxylation of certain bone proteins,
    rendering them nonfunctional.
                                           71
   Purple toe syndrome
   Another rare complication that may occur early
    during warfarin treatment (usually within 3 to 8 weeks)
    is purple toe syndrome. This condition is thought to
    result from small deposits of cholesterol breaking
    loose and flowing into the blood vessels in the skin of
    the feet, which causes a blueish purple color and
    may be painful. It is typically thought to affect the big
    toe, but it affects other parts of the feet as well,
    including the bottom of the foot (plantar surface).
    The occurrence of purple toe syndrome may require
    discontinuation of warfarin



                                                      72
   Warfarin consists of a racemic mixture of
    two activeenantiomers—R- and S-
    forms—each of which is cleared by
    different pathways. S-warfarin has five
    times the potency of the R-isomer with
    respect to vitamin K antagonism.




                                         73
   Warfarin is slower-acting than the common
    anticoagulantheparin, though it has a number of advantages.
    Heparin must be given by injection, whereas warfarin is available
    orally. Warfarin has a long half-life and need only be given once
    a day. Heparin can also cause a prothrombotic
    condition, heparin-induced thrombocytopenia (an antibody-
    mediated decrease in platelet levels), which increases the risk
    for thrombosis. It takes several days for Warfarin to reach the
    therapeutic effect since the circulating coagulation factors are
    not affected by the drug (thrombin has a half-life time of days).
    Warfarin's long half life means that it remains effective for several
    days after it was stopped. Furthermore, if given initially without
    additional anticoagulant cover, it can increase thrombosis risk
    (see below). For these main reasons, hospitalised patients are
    usually given heparin with warfarin initially, the heparin covering
    the 3-5 day lag period and being withdrawn after a few days.



                                                                 74

				
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