Forthyron 800 Microgram Tablet

Main information

  • Trade name:
  • Forthyron 800 Microgram Tablet
  • Pharmaceutical form:
  • Tablet
  • Medicine domain:
  • Animals
  • Medicine type:
  • Allopathic drug

Documents

Localization

  • Available in:
  • Forthyron 800 Microgram Tablet
    Austria
  • Language:
  • English

Therapeutic information

  • Therapeutic group:
  • levothyroxine sodium
  • Therapeutic area:
  • Dogs

Status

  • Source:
  • HMA - Europe
  • Authorization number:
  • UK/V/0387/002
  • Authorization date:
  • 26-10-2011
  • EU code:
  • UK/V/0387/002
  • Last update:
  • 09-08-2016

Summary of Product characteristics: dosage, interactions, side effects

Issued:November2011

AN:01161/2010

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SUMMARYOFPRODUCTCHARACTERISTICS

1. NAMEOFTHEVETERINARYMEDICINALPRODUCT

Forthyron600microgramtabletsfordogs

2. QUALITATIVEANDQUANTITATIVECOMPOSITION

Onetabletcontains:

600microgramlevothyroxinesodiumpertabletequivalentto583microgram

levothyroxine

Forafulllistofexcipients,seesection6.1

3. PHARMACEUTICALFORM

Tablet

Whitetooffwhiteroundtablets,scoredononeside

Thetabletsmaybedividedintohalvesorquarters.

4. CLINICALPARTICULARS

4.1. Targetspecies

Dogs.

4.2. Indicationsforuse,specifyingthetargetspecies

Forthetreatmentofhypothyroidismindogs.

4.3. Contra-indications

Donotuseindogssufferingfromuncorrectedadrenalinsufficiency.

Donotuseincasesofknownhypersensitivitytolevothyroxinesodium

4.4. Specialwarningsforeachtargetspecies

Thediagnosishypothyroidismshouldbeconfirmedwithappropriatetests.

4.5. Specialprecautionsforuse

Specialprecautionsforuseinanimals

Asuddenincreaseindemandforoxygendeliverytoperipheraltissues,plusthe

chronotropiceffectsoflevothyroxinesodium,mayplaceunduestressonapoorly

functioningheart,causingdecompensationandsignsofcongestiveheartfailure.

Hypothyroiddogssufferingfromhypoadrenocorticismhaveadecreasedabilityto

metaboliselevothyroxinesodiumandthereforeanincreasedriskofthyrotoxicosis.

Dogswithconcurrenthypoadrenocorticismandhypothyroidismshouldbestabilised

withglucocorticoidandmineralocorticoidtreatmentpriortotreatmentwithlevothyroxine

sodiumtoavoidprecipitatingahypoadrenocorticalcrisis.Afterthis,thyroidtests

shouldberepeated,thengradualintroductionoflevothyroxinetherapy,startingwith25%

ofthenormaldose,increasingby25%incrementseveryfortnightuntiloptimal

stabilisationisachievedisrecommended.Gradualintroductionoftherapyisalso

recommendedfordogswithotherconcurrentillnesses;particularlyindogswithcardiac

disease,diabetesmellitusandrenalorhepaticdysfunction.

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Specialprecautionstobetakenbythepersonadministeringthemedicinal

producttoanimals

Washhandsafteradministeringthetablets.Pregnantwomenshouldhandletheproduct

withcaution.Inthecaseofaccidentalingestion,seekmedicaladviceimmediatelyand

showthepackageleafletorthelabeltothephysician.Note:thisproductcontainsahigh

concentrationofL-thyroxinesodiumandmaypresentarisktohumans,inparticular

children,ifingested.

4.6. Adversereactions(frequencyandseriousness)

Restorationofphysicalactivitymayunmaskorintensifyotherproblems,suchas

osteoarthrosis.Adverseeffectsofthyroidhormonesaregenerallyassociatedwith

excessivedosageandcorrespondtothesymptomsofhyperthyroidism.Seealso

section4.10.

4.7. Useduringpregnancy,lactationorlay

Thesafetyoftheveterinarymedicinalproducthasnotbeenestablishedinpregnantor

lactatingbitches.However,levothyroxineisanendogenoussubstanceandthyroid

hormonesareessentialforthedevelopingfoetus,especiallyduringthefirstperiodof

gestation.Hypothyroidismduringpregnancymayresultinmajorcomplicationssuchas

foetaldeathandapoorperinataloutcome.Maintenancedoseoflevothyroxinesodium

mayneedadjustmentduringpregnancy.Pregnantbitchesshouldthereforebe

monitoredonaregularbasefromconceptionuntilseveralweeksafterdelivery.

4.8.Interactionswithothermedicinalproductsandotherformsofinteraction

Avarietyofdrugsmayimpairplasmaortissuebindingofthethyroidhormonesoralter

thyroidhormonemetabolism(eg.barbiturates,antacids,anabolicsteroids,diazepam,

furosemide,mitotane,phenylbutazone,phenytoin,propranolol,largedosesof

salicylates,andsulphonamides.).Whentreatingdogsthatarereceivingconcurrent

medicationthepropertiesofthesedrugsshouldbetakenintoconsideration.

Estrogensmayincreasethyroidrequirements.

Ketaminemaycausetachycardiaandhypertensionwhenusedinpatientsreceiving

thyroidhormones.Theeffectofcatecholaminesandsympaticomimeticsisincreasedby

levothyroxine.

Anincreaseinthedosageofdigitalismaybenecessaryinapatientthathadpreviously

compensatedcongestiveheartfailureandthatisplacedonthyroidhormone

supplementation.

Followingtreatmentofhypothyroidismindogswithconcurrentdiabetes,careful

monitoringofdiabeticcontrolisrecommended.

Mostdogsonchronichigh-dose,dailyglucocorticoidtherapywillhaveverylowor

undetectableserumT

concentrations,aswellassubnormalT

values.

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4.9 Amountstobeadministeredandadministrationroute

Therecommendedstartingdosageoflevothyroxinesodiumis10µg/kgbodyweight

orallyevery12hour.Becauseofvariabilityinabsorptionandmetabolism,thedosage

mayrequirealterationsbeforeacompleteclinicalresponseisobserved.Theinitial

dosageandfrequencyofadministrationaremerelyastartingpoint.Therapyhastobe

highlyindividualisedandtailoredtotherequirementsoftheindividualdog.When

initiatingdosingofdogsweighingless than5kgbodyweight,aquarterofone200μg

tabletshouldbeadministeredoncedaily.Suchcases

shouldbemonitoredcarefully.Inthedog,absorptionoflevothyroxinesodiummaybe

affectedbythepresenceoffood.Thetimingoftreatmentanditsrelationtofeeding

shouldthereforebekeptconsistentfromdaytoday.Toadequatelymonitortherapy,

troughvalues(justpriortotreatment)andpeakvalues(aboutthreehoursafterdosing)

ofplasmaT

canbemeasured.Inadequatelydoseddogspeakplasmaconcentration

ofT

shouldbeinthehigh-normalrange(approximately30to47nmol/l)andtrough

valuesshouldbeaboveapproximately19nmol/l.IfT

levelsareoutsidethisrangethe

levothyroxinedosecanbeadjustedin50to200µgincrementsuntilthepatientis

clinicallyeuthyroidandserumT

iswithinthereferencerange.PlasmaT

levelscanbe

retestedtwoweeksafterchangeofdosage,butclinicalimprovementisanequally

importantfactorindeterminingindividualdosageandthiswilltakefourtoeightweeks.

Whentheoptimumreplacementdosehasbeenattained,clinicalandbiochemical

monitoringmaybeperformedevery6 –12months.

Tobreakatabletaccuratelyandeasily,placethetabletscoreside

upandapplypressurewithyourthumb.

Tobreakthetabletintwoparts;holdonehalfofthetabletdownandpressdownthe

otherhalf.

4.10.Overdose(symptoms,emergencyprocedures,antidotes),ifnecessary

Followingadministrationofoverdosesthyrotoxicosiscouldoccur.Thyrotoxicosisasa

sideeffectofmildoversupplementationisuncommonindogs,owingtothecanine

abilitytocatabolizeandexcretethyroidhormones.Incaseofaccidentalintakeoflarge

amountsoftheveterinarymedicinalproductabsorptioncanbedecreasedbyinduction

ofvomitingandoraladministrationofbothactivatedcharcoalandmagnesiumsulphate

once.

Overdosesofthreeuptosixtimeslabelrecommendedstartingdosefor4consecutive

weeksinhealthy,euthyroiddogsresultedinnosignificantclinicalsignsthatcouldbe

attributedtotreatment.Singleoverdoseupto3-6xtherecommendeddosedoesnot

poseathreattothedog,andnoactionsarenecessary.However,followingchronic

over-supplementation,clinicalsignsofhyperthyroidismsuchaspolydipsia,polyuria,

panting,weightlosswithoutanorexia,andeitherorbothtachycardiaandnervousness

maytheoreticallyoccur.ThepresenceofthesesignsshouldresultinevaluationofT

serumconcentrationstoconfirmthediagnosis,andimmediatediscontinuanceofthe

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supplementation.Oncethesignshaveabated(daystoweeks),thethyroiddosagehas

beenreviewed,andtheanimalhasfullyrecovered,alowerdosagemaybeinstituted,

withtheanimalbeingmonitoredclosely.

4.11.Withdrawalperiods

Notapplicable.

5. PHARMACOLOGICALPROPERTIES

Pharmacotherapeuticgroup:syntheticthyroidhormones

ATCvetcode:QH03AA01.

5.1. Pharmacodynamicproperties

Pharmacologicallylevothyroxineisclassifiedasahormonalpreparationthatreplaces

deficientendogenoushormones.

LevothyroxineT

isconvertedtotriiodothyronineT

actsoncellularprocessesvia

specificligand-receptorinteractionswiththenucleus,themitochondria,andtheplasma

membrane.InteractionofT

withbindingsitesleadstoaugmentedtranscriptionofDNA

ormodulationofRNA,thusinfluencingproteinsynthesisandenzymeaction.

Thyroidhormonesactonmanydifferentcellularprocesses.Indevelopinganimalsand

humanbeings,theyarecrucialdeterminantsofnormaldevelopment,especiallyinthe

centralnervoussystem.Thyroidsupplementationincreasesbasalcellularmetabolism

andoxygenconsumptiontherebyaffectingthefunctionofvirtuallyallorgansystems.

5.2. Pharmacokineticparticulars

SomedogsappearedtoconsistentlyeitherabsorbL-thyroxinebetterand/oreliminateit

moreslowlythandootherdogs.Furthermoreabsorptionandeliminationrateis

influencedbydailyintakeoflevothyroxinesodium(highabsorption/loweliminationin

caseoflowintakeandviceversaincaseofhighintake).Thevariabilityin

pharmacokineticparametersbetweenindividualdogsisconsiderableand,althoughthe

presenceoffoodmayaffectabsorption,itisconsideredtohaveaminoreffectonthe

parametersoverall.Absorptionisrelativelyslowandincomplete:InmostcasesT

occursbetween1to5hoursafteroraladministration,meanC

variesmorethan3

foldbetweendogsonthesamedoses.Inadequatelydoseddogstheplasmapeak

approachesorslightlyexceedstheupperlimitofnormalplasmaT

levels,andbythe

endof12hoursafteroraladministration,plasmaT

usuallydeclinestothelowerhalfof

thenormalrange.TheratesofdisappearanceofT

fromtheplasmaareslowedin

hypothyroidism.Alargepartofthethyroxineistakenupbytheliver.L-thyroxineisbound

toplasma-proteinsandplasmalipoproteins.Partofadoseofthyroxineismetabolised

tothemorepotenttriiodothyronine(T

)bydeiodination.Theprocessofdeiodination

continues.Thesefurtherdeiodinatedmetabolicproducts(otherthanT

andT

)donot

havethyromimeticactivity.Otherpathwaysofthyroidhormonemetabolisminclude

conjugationtoformsolubleglucuronidesandsulphatesforbiliaryorurinaryexcretionas

wellascleavageoftheetherlinkageoftheiodothyroninemolecule.Inthedog,over

50%oftheT

producedeachdayarelostinthefaeces.Theextrathyroidalbodystores

ofT

areeliminatedandreplacedinabout1day.

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6. PHARMACEUTICALPARTICULARS

6.1. Listofexcipients

Calciumhydrogenphosphatedihydrate,

Cellulose,Microrcrystalline,

SodiumStarchGlycolate(typeA),

Magnesiumstearate.

6.2. Incompatibilities

Notapplicable

6.3. Shelf-life

Shelf-lifeoftheveterinarymedicinalproductaspackagedforsale:2years

Shelf-lifeofremainingtabletparts:4days

6.4. Specialprecautionsforstorage

Donotstoreabove25°C.

Returnanydividedtablettotheopenedblisterandusewithin4days

6.5. Natureandcontentsofimmediatepackaging

Blisters,consistingofaluminiumfoilandawhite,opaquePVC/PE/PVDCfoil.

10Tabletsperblister,5or25blisterspercarton,50or250tabletspercarton.

Notallpacksizesmaybemarketed.

6.6. Specialprecautionsforthedisposalofunusedveterinarymedicinal

productorwastematerials,derivedfromtheuseofsuchproductsif

appropriate.

Anyunusedveterinarymedicinalproductorwastematerialsderivedfromsuch

veterinarymedicinalproductsshouldbedisposedofinaccordancewithlocal

requirement.

7. MARKETINGAUTHORISATIONHOLDER

EurovetAnimalHealthB.V.

Handelsweg25,5531AEBladel

TheNetherlands

8. MARKETINGAUTHORISATIONNUMBER

Vm16849/4038

9. DATEOFFIRSTAUTHORISATION

15November2011

10. DATEOFREVISIONOFTHETEXT

November2011