The Childrens Hospital

Being on WarfarinInformation for parents and children

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ContentsWhatiswarfarin?

Thecoagulation(bloodclotting)system

Howwarfarinworks

TheINRtest

Whyyoumightneedtotakewarfarin

Warfarintabletsavailable

Whatarethesideeffectsofwarfarin?

Effectsofotherdrugs,lifestyleanddietontheINRandwarfarintherapy

Sports

Whattodoifyouhaveaninjury

Generalhealthandsafety

Growingup

Howtocontactus

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Whatiswarfarin?Warfarinisadrugthatcanbegiventoyoungpeopleiftheyare:

Atriskofformingabloodclot

Orhavedevelopedaclotandneedtreatment.

Warfarinisananticoagulanttablettakenbymouthandworksbyincreasingthetimetakenforyourbloodtoclot.

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Thecoagulation(bloodclotting)systemThehumanbodydependsonthebloodcirculatingallthetimetoprovideitsorgans(e.g.theheart,brain,skin)withoxygenandnourishment.Tokeepthebloodflowingwellitneedstobeofacertainconsistency.Italsoneedstobeabletopluganyleaksthatmayoccur,likewhenyoucutyourfinger.

Thewallofthedamagedbloodvesselissealedoffbyatinybloodclot(sometimescalledathrombus).Thisclotisformedasaresultofproteinsthatcirculateinthebloodinadissolvedform.Whenaninjuryoccurstheproteinsgointoactiontoformabloodclot.Thisisanaturalprocessandnecessarytostayingoodhealth.

Ifaclotformswhenitshouldnt,itcanbecarriedinthebloodtootherpartsofthebody(embolism)andthiscanthenleadtoseriousproblems,e.g.stroke.Thisisthereasonforthebloodthinningtreatment.

HowwarfarinworksWarfarinworksbyslowingthebloodclottingprocessdown.Itpreventstheclottingproteins(vitaminK)fromdoingtheirjobfully.VitaminKispresentinfoodandmilk(seesectionondiet),andisusedtotreatoverdosesofwarfarinorinpeoplewhohaveahighINR(clottinglevel).Youmayhavenoticedthatonceyouareonwarfarin,whenyoucutyourselfittakesalittlelongertostopbleeding.

Everybodyreactsdifferentlytowarfarinsothedosemustbeworkedouteachtimeforeverypatient.

Theactionofthetabletscanlastquitealongtimeinthebody;ittakesabout3-4daystoseeaneffect.Thismeansthatachangeindosewillnotbereflectedinthebloodtestuntil3-4dayslater.Theonlywaytotesttheeffectivenessofthetreatmentisbytakingabloodsampleandseeinghowlongittakestoclot.

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WhyyoumightneedtotakewarfarinWithsomediseasesormedicalproblemsbloodclotsareproducedmoreeasilythannormal.Theseinclude: Cardiomyopathy(heartmuscleproblem) Afterinsertionofanartificialheartvalves Someheartoperations,e.g.Fontanprocedure

Yourdoctorhasputyouonanticoagulanttreatmentbecauseofoneoftheseconditions.

TheINRtestMeasuring the INRTheunitofmeasurementusediscalledtheINR(InternationalNormalisedRatio).Thisissimplyanumericalscale.

The normal measurement is about 1Thehigherthenumber,thelongerittakesthebloodtoclot!

Warfarin and target INRWewilltryandkeepyourbloodclottingtowithinacertainnumericaltarget(number)dependingonyourmedicalcondition.ThisisknownasthetargetINR.Mostcommontargetsare2to3or2.5to3.5.unitsofINR.WetrytokeeptheINRwithinasaferange(sometimesknownasatherapeuticrange)asmanythingscanaffecthowwarfarinworksinthebody,(drugs,diet,illhealth)andmanychildrenwillnotbeintheirrange100%ofthetime,whichiswhyregularbloodtestsarenecessary.

Frequency of blood testsAbloodtestisrequiredregularlytocheckthattheINRleveliswithinthetargetrange.IfyouareunwellorstartanynewmedicinesweusuallyaskforabloodtesttocheckifthishasaffectedtheINRlevel.Ifthewarfarindoseisadjustedabloodtestisrequiredsoonafterwardstochecktheeffect.IftheINRis

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toolowawarfarindosemayneedtobeincreased,ifitstoohighadosemayneedtobedecreasedormissed.

Pleasedonotadjustyourwarfarindosewithouttheadviceoftheanticoagulationteammanagingyourtreatment.

Warfarintabletsavailable: 0.5 mg white 1mg brown

3mg blue 5mg pink

Whatarethesideeffectsofwarfarin?OverdoseThefollowingcanbesignsofoverdose(toomuchWarfarin): Haemorrhageisthemajorsideeffectofwarfarin!Seekurgentmedicalattentionifmajorbleeding.

AhighINR(>5) Heavilybleedinggums Heavyperiods Bruisesfornoreason Nosebleedsthatlastlongerthan10minutesorregularnosebleeds

Bloodintheurine Coffeegroundoranybloodstainedvomitorthepassingofblackorbloodystools.

IfyouobserveanyofthesesignsorotherunexpectedorunexplainedsignsyoushoulddoanINRcheckandaskyourdoctorforadvice.

Too little Warfarin (signs of clotting) LowINR(