#28 Anticoagulant Therapy

8/9/2019 #28 Anticoagulant Therapy

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Monitoring the Traditional & theMonitoring the Traditional & the

New AnticoagulantsNew Anticoagulants

Michael J. Sanfelippo, M.S.Michael J. Sanfelippo, M.S.

Technical Director, Coagulation ServicesTechnical Director, Coagulation ServicesMarshfield LabsMarshfield Labs


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Anticoagulants to be DiscussedAnticoagulants to be Discussed

HeparinHeparin

WarfarinWarfarin

Low Molecular Weight heparinLow Molecular Weight heparin FonaparienuxFonaparienux

Direct Thrombin InhibitorDirect Thrombin Inhibitor


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Unfractionated Heparin ChemicalUnfractionated Heparin Chemical

CompositionComposition Sulfated glycosaminoglycanSulfated glycosaminoglycan

Polysaccharide chains with moleculr weights ofPolysaccharide chains with moleculr weights of

30,00030,000 100,000100,000 Chains alternating NChains alternating N--acetylglucosamine andacetylglucosamine and

glucuronic acidglucuronic acid

Purified heparin polysaccharide chains of 3,000Purified heparin polysaccharide chains of 3,000 35,000 with average molecular weight of35,000 with average molecular weight of

12,00012,000


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Pharmacokinetics of HeparinPharmacokinetics of Heparin

Intravenous administrationIntravenous administration immediateimmediate

anticoagulation half life of one houranticoagulation half life of one hour

anticoagulant effect for 2anticoagulant effect for 2 6 hours6 hours Subcutaneous administrationSubcutaneous administration peakpeak

anticoagulation at 4 hours with effect up to 12anticoagulation at 4 hours with effect up to 12

hourshours

In high doses, most is excreted in the urineIn high doses, most is excreted in the urineunalteredunaltered


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Use of HeparinUse of Heparin

Immediate anticoagulantImmediate anticoagulant

Activity is variable requires monitoringActivity is variable requires monitoring

Used for initial treatment of DVT and PEUsed for initial treatment of DVT and PE Used in open heart surgeryUsed in open heart surgery

Used to cap intravenous linesUsed to cap intravenous lines


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Factors Affecting AnticoagulantFactors Affecting Anticoagulant

EffectEffect Level of AntithrombinLevel of Antithrombin

Heparin binding to acute phase proteinsHeparin binding to acute phase proteins

Release of platelet factor 4Release of platelet factor 4


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Monitoring HeparinMonitoring Heparin

Therapeutic range 0.3Therapeutic range 0.3 0.7 units/ml0.7 units/ml

Specific heparin assay, inhibition of XaSpecific heparin assay, inhibition of Xa

measured with chromogenic substratemeasured with chromogenic substrateAPTTAPTT


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Establishment of Therapeutic RangeEstablishment of Therapeutic Range

for APTTfor APTT

BrillBrill--Edwards MethodEdwards Method Measure heparin level in at least 30 patients on heparin only.Measure heparin level in at least 30 patients on heparin only.

Do APTTs on all specimensDo APTTs on all specimens

Calculate dose response curve by regression analysisCalculate dose response curve by regression analysis Therapeutic range is APTT range that corresponds to 0.3Therapeutic range is APTT range that corresponds to 0.3

0.7 units/ml0.7 units/ml

Determined from dose response curve using regressionDetermined from dose response curve using regressionanalysisanalysis

Problems for small hospitalProblems for small hospital Getting enough patientsGetting enough patients

Doing heparin assayDoing heparin assay


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Example of BrillExample of Brill--Edwards MethodEdwards MethodSpecimenSpecimen APTTAPTT HeparinHeparin

11 2525 0.150.15

22 4545 0.380.38

33 5555 0.450.4544 8888 0.850.85

55 7575 0.700.70

66 6565 0.550.55

77 3535 0.250.25

88 4747 0.350.35

99 6868 0.720.72

1010 9898 0.920.92


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BrillBrill--Edwards cont . . .Edwards cont . . .

APTT at 0.30 unitsAPTT at 0.30 units 47 sec47 sec

APTT at 0.7 unitAPTT at 0.7 unit 75 sec75 sec

Thus therapeutic range is 47Thus therapeutic range is 47 75 sec approximate75 sec approximate


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Specific Heparin AssaySpecific Heparin Assay

Based on inhibition of XaBased on inhibition of Xa

Heparin forms complex with antithrombinHeparin forms complex with antithrombin

(heparin(heparin--AT)AT) HeparinHeparin--At +XaAt +Xa ATAT--Xa + XaXa + Xa

Free Xa + chromogenicFree Xa + chromogenic substrate peptidesubstrate peptide

+Paranitroanaline+Paranitroanaline


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Heparin AssayHeparin Assay


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Adverse Effects ofProtamine SulfateAdverse Effects ofProtamine Sulfate

HemorrhageHemorrhage

Allergic reactionAllergic reaction


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Heparin Induced ThrombocytopeniaHeparin Induced Thrombocytopenia

Type I Platelet count drops slightly but returnsType I Platelet count drops slightly but returns

to normal while heparin is continuedto normal while heparin is continued--notnotantibody mediatedantibody mediated

Type II Severe antibody mediatedType II Severe antibody mediatedthrombocytopenia with life threatening arterialthrombocytopenia with life threatening arterial

and venous thrombosis if heparin is continuedand venous thrombosis if heparin is continued


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Heparin Induced ThrombocytopeniaHeparin Induced Thrombocytopenia

Type IIType II Potentially fatal complication of heparin therapyPotentially fatal complication of heparin therapy

due to the development of a heparin dependentdue to the development of a heparin dependentantibody against platelet factor 4antibody against platelet factor 4

Thrombocytopenia results from activation ofThrombocytopenia results from activation ofplatelets by complex of IgG, heparin, andplatelets by complex of IgG, heparin, and

platelet factor 4platelet factor 4

Platelet activation causes release of ADP whichPlatelet activation causes release of ADP whichcauses platelet aggregate formationcauses platelet aggregate formation


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Diagnostic Features of HIT Type IIDiagnostic Features of HIT Type II

Platelet count of less than 100,000/mmPlatelet count of less than 100,000/mm33 oror

count of less that 50% of the platelet countcount of less that 50% of the platelet countbefore heparin was startedbefore heparin was started

Occurs 5Occurs 5 12 days after heparin is started12 days after heparin is started

Abnormal results in tests for antibody to plateletAbnormal results in tests for antibody to platelet

factor 4 or heparin mediated platelet activationfactor 4 or heparin mediated platelet activation

Occurrence of arterial or venous thrombusOccurrence of arterial or venous thrombus

formation while on heparinformation while on heparin


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Tests for HIT Type IITests for HIT Type II

Elisa assay for antibody to platelet factor 4Elisa assay for antibody to platelet factor 4

Release of radioRelease of radio--labeled serotonin from normallabeled serotonin from normal

donor plateletsdonor platelets Daily platelet counts recommended for allDaily platelet counts recommended for all

patients on heparinpatients on heparin


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Treatment of HITTreatment of HIT Type IIType II

Stop heparinStop heparin

Use direct thrombin inhibitorsUse direct thrombin inhibitors

ArgatrobanArgatroban Lepiruden (RefludenLepiruden (Refluden))

Warfarin is contraindicatedWarfarin is contraindicated


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Low Molecular WeightLow Molecular Weight

HeparinHeparin


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Low Molecular Weight HeparinLow Molecular Weight Heparin

Made by enzymatic or chemicalMade by enzymatic or chemical

depolymerizationdepolymerization

Lower molecular weight 4,000Lower molecular weight 4,000 5,0005,000 Loss of most anti IIa activity but retain anti XaLoss of most anti IIa activity but retain anti Xa

Predicable anticoagulant activityPredicable anticoagulant activity


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Administration and Monitoring LowAdministration and Monitoring Low

Molecular Weight HeparinsMolecular Weight Heparins Given subcutaneouslyGiven subcutaneously

Peak level at 4 hours post injectionPeak level at 4 hours post injection

Half life of 4.5 hours with significant activity atHalf life of 4.5 hours with significant activity at12 hours12 hours


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Laboratory Monitoring LowLaboratory Monitoring Low

Molecular Weight HeparinMolecular Weight Heparin Usually not requiredUsually not required

Assayed by inhibition of Xa using aAssayed by inhibition of Xa using a

chromogenic substratechromogenic substrate Same assay as unfractionated heparin butSame assay as unfractionated heparin but

different calibratordifferent calibrator

APTT not reliable but may be slightly prolongedAPTT not reliable but may be slightly prolonged


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Conditions Requiring Monitoring ofConditions Requiring Monitoring of

Low Molecular Weight Heparin

Low Molecular Weight Heparin

Patients with renal insufficiencyPatients with renal insufficiency

Exceptionally large or small patientsExceptionally large or small patients

Newborn and childrenNewborn and children


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Low Molecular Weight Heparins inLow Molecular Weight Heparins in

CommonU

seCommonU

se Enoxaparin (LovenoxEnoxaparin (Lovenox))

Daltaparin (FragminDaltaparin (Fragmin))

Both calibrated against the same standardBoth calibrated against the same standard


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WarfarinWarfarin


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Action of WarfarinAction of Warfarin

Inhibits vitamin K epoxide reductaseInhibits vitamin K epoxide reductase

Prevents attachment of glutamic acid residues toPrevents attachment of glutamic acid residues to

factors II, VII, IX, X, protein C, and proteinS

factors II, VII, IX, X, protein C, and proteinS

Glutamic acid residues necessary for factor toGlutamic acid residues necessary for factor tobind to catalytic phospholipid surfacesbind to catalytic phospholipid surfaces


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Methods of MonitoringMethods of Monitoring

Accepted method is one stage prothrombin timeAccepted method is one stage prothrombin time

Assay of factor X with chromogenic substrateAssay of factor X with chromogenic substrate

for special conditionsfor special conditionsTraditional clotting assay of factor XTraditional clotting assay of factor X


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HalfHalf--Lives of Vitamin K DependentLives of Vitamin K Dependent

F

actorsF

actorsIIII 60 Hours60 Hours

VIIVII 44 6 Hours6 Hours

IXIX 2020 24 Hours24 Hours

XX 4848 72 Hours72 Hours

Protein CProtein C 8 Hours8 Hours

Protein SProtein S 30 Hours30 Hours


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Monitoring Warfarin withMonitoring Warfarin with

Prothrombin TimeP

rothrombin Time Reported as International Normalized RationReported as International Normalized Ration

(INR)(INR)

Reporting as clotting time in seconds only is notReporting as clotting time in seconds only is notacceptableacceptable


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INRINR

Calculated by the formalaCalculated by the formala

INR = Patient Time (sec)/Normal Mean Time(sec) ISCINR = Patient Time (sec)/Normal Mean Time(sec) ISC

Where ISC = International Sensitivity IndexWhere ISC = International Sensitivity Index

Test Plasma Time (sec)

Mean Normal Plasma TimeINR

ISI


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Use of the Chromogenic Factor XUse of the Chromogenic Factor X

AssayAssay Patients with the lupus anticoagulantPatients with the lupus anticoagulant

Patients with abnormal fibrinogen and problemPatients with abnormal fibrinogen and problem

in detection of fibrin endpointin detection of fibrin endpointTherapeutic range 43% to 17% correspondes toTherapeutic range 43% to 17% correspondes to

INR 2.0INR 2.0 3.53.5


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The Assay ofFactor X with aThe Assay ofFactor X with a

ChromogenicS

ubstrateChromogenicS

ubstrate Factor X is activated by Russells Viper VenomFactor X is activated by Russells Viper Venom

and Ca++and Ca++

Factor Xa hydrolyses substrate (S

2765)Factor Xa hydrolyses substrate (S

2765)liberating paranitroanalineliberating paranitroanaline

Optical density read at 405 nmOptical density read at 405 nm--directly related todirectly related to

factor X concentrationfactor X concentration


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Effect ofLupus Anticoagulant onEffect ofLupus Anticoagulant on

Prothrombin TimeP

rothrombin Time May bind phospholipid in test reagentMay bind phospholipid in test reagent

May also bind prothrombinMay also bind prothrombin


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Case History ofPatient withCase History ofPatient with

AbnormalF

ibrinogenAbnormalF

ibrinogen 65 year old female with atrial fibrillation on65 year old female with atrial fibrillation on

warfarin for several years with good controlwarfarin for several years with good control

Had INR performed at a different lab with aHad INR performed at a different lab with avalue of > 11.0value of > 11.0

Warfarin stoppedWarfarin stopped

Warfarin restarted with INRs at original labWarfarin restarted with INRs at original lab

acceptableacceptable INR performed at different lab with > 11.0INR performed at different lab with > 11.0

againagain


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Case History cont . . .Case History cont . . .

Duplicate specimens drawnDuplicate specimens drawn

Original lab INR 1.3Original lab INR 1.3

Other lab INR > 11.0Other lab INR > 11.0

Chromogenic X 79% (Normal 65Chromogenic X 79% (Normal 65 165%)165%)

Thrombin time 21.6 sec (16.4Thrombin time 21.6 sec (16.4 20.7 sec)20.7 sec)

Fibrinogen 642 mg/dl (174Fibrinogen 642 mg/dl (174--442 mg/dl)442 mg/dl)

Fibrinogen antigen 750 mg/dl (180Fibrinogen antigen 750 mg/dl (180 310 mg/dl)310 mg/dl)

Reptilase time 16.1 sec (15.5Reptilase time 16.1 sec (15.5 19.0 sec)19.0 sec)

Similar to Fibrinogen LongmontSimilar to Fibrinogen Longmont


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Adverse Affects of WarfarinAdverse Affects of Warfarin

Bleeding, anticoagulation reversal by vitamin KBleeding, anticoagulation reversal by vitamin K

Tissue necrosisTissue necrosis

Occurs in patients with underlying protein C orSOccurs in patients with underlying protein C orSdeficiency prevented by giving small loading dose ofdeficiency prevented by giving small loading dose of

22 5 mg/day starting warfarin while patient is on5 mg/day starting warfarin while patient is onheparinheparin


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Effect ofUnfractionated Heparin onEffect ofUnfractionated Heparin on

INRINR Heparin can prolong the prothrombin timeHeparin can prolong the prothrombin time

(increase INR)(increase INR)

Most reagents now contain a heparin antagonistMost reagents now contain a heparin antagonistprotamine sulfate or polybreneprotamine sulfate or polybrene

Most reagents will neutralize up to 1.0 units/mlMost reagents will neutralize up to 1.0 units/ml


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FondaparinuxFondaparinux


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Chemistry and Action ofChemistry and Action of

F

ondaparinuxF

ondaparinuxA pentasaccharide with a molecular weight ofA pentasaccharide with a molecular weight of

1,728 daltons1,728 daltons

Anticoagulates by accelerating the binding ofAnticoagulates by accelerating the binding ofantithrombin to Xaantithrombin to Xa

Has no effect on thrombin bindingHas no effect on thrombin binding


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Therapeutic Levels for FondaparinuxTherapeutic Levels for Fondaparinux

Administered by subcutaneous injectionsAdministered by subcutaneous injections

Peak level at 3 hour post injectionPeak level at 3 hour post injection

Half life 14Half life 14 20 hours, once per day dosing20 hours, once per day dosing


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Fondaparinux Used for ProphylaxisFondaparinux Used for Prophylaxis

2.5 mg daily2.5 mg daily

Peak level 0.39Peak level 0.39 0.50 mg/L0.50 mg/L


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Fondaparinux Used for Treatment ofFondaparinux Used for Treatment of

Deep Venous Thrombosis orDeep Venous Thrombosis or

Pulmonary EmbolismPulmonary Embolism

50 kg body weight 5.0 mg once/day50 kg body weight 5.0 mg once/day

5050 100 kg body weight 7.5 mg/day100 kg body weight 7.5 mg/day

Over 100 kg body weight 10.0 mg/dayOver 100 kg body weight 10.0 mg/day

Anticipated peak plasma levels 1.20Anticipated peak plasma levels 1.20 1.26 mg/L1.26 mg/L


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Methods of MonitoringMethods of Monitoring

Common laboratory tests, prothrombin time andCommon laboratory tests, prothrombin time andactivated partial thromboplastin time are insensitive toactivated partial thromboplastin time are insensitive tofondaparinuxfondaparinux

Specific assay based on inhibition of Xa with calibrationSpecific assay based on inhibition of Xa with calibrationcurve using fondaparinuxcurve using fondaparinux

Monitoring generally not required due to theMonitoring generally not required due to thepredictability of the drugs anticoagulant actionpredictability of the drugs anticoagulant action

Should be monitored in patients with renal impairmentShould be monitored in patients with renal impairment

and elderly patients (over 75 years)and elderly patients (over 75 years) Should be monitored in patients less than 50 kg bodyShould be monitored in patients less than 50 kg body

weightweight


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Advantages ofFondaparinuxAdvantages ofFondaparinux

Long half lifeLong half life

Low incidence of HIT, may be used to treatLow incidence of HIT, may be used to treat

patient who have suffered HITpatient who have suffered HIT Generally doesnt require monitoringGenerally doesnt require monitoring


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ArgatrobanArgatroban

A small molecule molecular weight of 526A small molecule molecular weight of 526

Derived from arginineDerived from arginine

Inhibits by reversibly binding to thrombinInhibits by reversibly binding to thrombinindependent of antithrombinindependent of antithrombin

Half life of 39Half life of 39 51 minutes51 minutes


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Therapeutic Levels and MonitoringTherapeutic Levels and Monitoring

Given by continuous infusionGiven by continuous infusion

Monitor with activated partial thromboplastin timeMonitor with activated partial thromboplastin time(APTT)(APTT)

At 2 hour of infusion target APTT range is 1.5At 2 hour of infusion target APTT range is 1.5 3.03.0times baselinetimes baseline

ArgatrobanArgatrobanwill prolong prothrombin time (PT)will prolong prothrombin time (PT)

Use chromogenic assay factor X to monitor warfarinUse chromogenic assay factor X to monitor warfarinduring transition from argatroban to warfarinduring transition from argatroban to warfarin


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Drug Use and Adverse AffectsDrug Use and Adverse Affects

Primary use to treat patients with HITPrimary use to treat patients with HIT

Hemorrhage is the only major adverse affectHemorrhage is the only major adverse affect

No known antidoteNo known antidote


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Lepiruden (RefludenLepiruden (Refluden))


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Therapeutic Levels and MonitoringTherapeutic Levels and Monitoring

Monitored by APTTMonitored by APTT

General target range 1.5General target range 1.5 2.5 baseline APTT2.5 baseline APTT


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Adverse Affects ofLepirudenAdverse Affects ofLepiruden

HemorrhageHemorrhage

No known antidoteNo known antidote

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#28 Anticoagulant Therapy