Forthyron 200

Main information

  • Trade name:
  • Forthyron 200
  • Pharmaceutical form:
  • Tablet
  • Medicine domain:
  • Animals
  • Medicine type:
  • Allopathic drug

Documents

Localization

  • Available in:
  • Forthyron 200
    Greece
  • Language:
  • English

Therapeutic information

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

Status

  • Source:
  • HMA - Europe
  • Authorization number:
  • UK/V/0217/001
  • Authorization date:
  • 14-07-2010
  • EU code:
  • UK/V/0217/001
  • Last update:
  • 09-08-2016

Summary of Product characteristics: dosage, interactions, side effects

Revised:October2010

AN:01014/2009

1. NAMEOFTHEVETERINARYMEDICINALPRODUCT

Forthyron200microgramtablet

2. QUALITATIVEANDQUANTITATIVECOMPOSITION

ActiveSubstance:

200µglevothyroxinesodiumpertabletequivalentto194µglevothyroxine

Forafulllistofexcipients,seesection6.1

3. PHARMACEUTICALFORM

Tablet

Whitetooffwhiteroundtablets,scoredononeside

Tabletsdivisibleinto4parts

4. CLINICALPARTICULARS

4.1. Targetspecies

Dogs.

4.2. Indicationsforuse,specifyingthetargetspecies

Forthetreatmentofhypothyroidismindogs.

4.3. Contra-indications

Donotuseindogssufferingfromuncorrectedadrenalinsufficiency.

4.4. Specialwarningsforeachtargetspecies

Thediagnosishypothyroidismshouldbeconfirmedwithappropriatetests.

4.5. Specialprecautionsforuse

Specialprecautionsforuseinanimals

Asuddenincreaseindemandforoxygendeliverytoperipheraltissues,plusthechronotropic

effectsoflevothyroxinesodium,mayplaceunduestressonapoorlyfunctioningheart,causing

decompensationandsignsofcongestiveheartfailure.Hypothyroiddogssufferingfrom

hypoadrenocorticismhaveadecreasedabilitytometaboliselevothyroxinesodiumand

thereforeanincreasedriskofthyrotoxicosis.Dogswithconcurrenthypoadrenocorticismand

hypothyroidismshouldbestabilisedwithglucocorticoidandmineralocorticoidtreatmentprior

totreatmentwithlevothyroxinesodiumtoavoidprecipitatingahypoadrenocorticalcrisis.

Afterthis,thyroidtestsshouldberepeated,thengradualintroductionoflevothyroxinetherapy,

startingwith25%ofthenormaldose,increasingby25%incrementseveryfortnightuntil

optimalstabilisationisachievedisrecommended.Gradualintroductionoftherapyisalso

recommendedfordogswithotherconcurrentillnesses;particularlydiabetesmellitusandrenal

orhepaticdysfunction.

Specialprecautionstobetakenbythepersonadministeringthemedicinalproduct

toanimals

Washhandsafteradministeringthetablets.Pregnantwomenshouldhandletheproductwith

caution.

Revised:October2010

AN:01014/2009

4.6. Adversereactions(frequencyandseriousness)

Restorationofphysicalactivitymayunmaskorintensifyotherproblems,suchas

osteoarthrosis.Adverseeffectsofthyroidhormonesaregenerallyassociatedwithexcessive

dosageandcorrespondtothesymptomsofhyperthyroidism.Seealsosection4.10.

4.7. Useduringpregnancy,lactationorlay

Thesafetyofuseoftheproductduringpregnancyhasnotbeenestablishedthroughspecial

reproductionstudies.However,levothyroxineisanendogenoussubstanceandthyroid

hormonesareessentialforthedevelopingfoetus,especiallyduringthefirstperiodof

gestation.Hypothyroidismduringpregnancymayresultinmajorcomplicationssuchasfoetal

deathandapoorperinataloutcome.Maintenancedoseoflevothyroxinesodiummayneed

adjustmentduringpregnancy.Pregnantbitchesshouldthereforebemonitoredonaregular

basefromconceptionuntilseveralweeksafterdelivery.

4.8. Interactionswithothermedicinalproductsandotherformsofinteraction

Avarietyofdrugsmayimpairplasmaortissuebindingofthethyroidhormonesoralterthyroid

hormonemetabolism(eg.barbiturates,antacids,anabolicsteroids,diazepam,furosemide,

mitotane,phenylbutazone,phenytoin,propranolol,largedosesofsalicylates,and

sulphonamides.).Whentreatingdogsthatarereceivingconcurrentmedicationtheproperties

ofthesedrugsshouldbetakenintoconsideration.

Anincreaseinthedosageofdigitalismaybenecessaryinapatientthathadpreviously

compensatedcongestiveheartfailureandthatisplacedonthyroidhormonesupplementation.

Estrogensmayincreasethyroidrequirements.

Ketaminemaycausetachycardiaandhypertensionwhenusedinpatientsreceivingthyroid

hormones.Theeffectofcatecholaminesandsympaticomimeticsisincreasedby

levothyroxine.

Followingtreatmentofhypothyroidismindogswithconcurrentdiabetes,carefulmonitoringof

diabeticcontrolisrecommended.

Mostdogsonchronichigh-dose,dailyglucocorticoidtherapywillhaveverylowor

undetectableserumT

concentrations,aswellassubnormalT

values.

4.9 Amountstobeadministeredandadministrationroute

Therecommendedstartingdosageoflevothyroxinesodiumis10µg/kgbodyweightorally

every12hour.Becauseofvariabilityinabsorptionandmetabolism,thedosagemayrequire

alterationsbeforeacompleteclinicalresponseisobserved.Theinitialdosageandfrequency

ofadministrationaremerelyastartingpoint.Therapyhastobehighlyindividualisedand

tailoredtotherequirementsoftheindividualdog.Wheninitiatingdosingofdogsweighing

lessthan5kgbodyweight,aquarterofone200μgtabletshouldbeadministeredoncedaily.

Suchcases

shouldbemonitoredcarefully.Inthedog,absorptionoflevothyroxinesodiummaybeaffected

bythepresenceoffood.Thetimingoftreatmentanditsrelationtofeedingshouldthereforebe

keptconsistentfromdaytoday.Toadequatelymonitortherapy,troughvalues(justpriorto

treatment)andpeakvalues(aboutthreehoursafterdosing)ofplasmaT

canbemeasured.In

adequatelydoseddogspeakplasmaconcentrationofT

shouldbeinthehigh-normalrange

Revised:October2010

AN:01014/2009

(approximately30to47nmol/l)andtroughvaluesshouldbeaboveapproximately19nmol/l.If

levelsareoutsidethisrangethelevothyroxinedosecanbeadjustedin50to200µg

incrementsuntilthepatientisclinicallyeuthyroidandserumT

iswithinthereferencerange.

PlasmaT

levelscanberetestedtwoweeksafterchangeofdosage,butclinicalimprovement

isanequallyimportantfactorindeterminingindividualdosageandthiswilltakefourtoeight

weeks.Whentheoptimumreplacementdosehasbeenattained,clinicalandbiochemical

monitoringmaybeperformedevery6 –12months.

Tobreaka200µgtabletaccuratelyandeasily,placethetablet

scoresideupandapplypressurewithyourthumb.

Tobreakthetabletintwoparts;holdonehalfofthetabletdownandpressdowntheotherhalf.

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

Followingadministrationofoverdosesthyrotoxicosiscouldoccur.Thyrotoxicosisasaside

effectofmildoversupplementationisuncommonindogs,owingtothecanineabilityto

catabolizeandexcretethyroidhormones.Incaseofaccidentalintakeoflargeamountsof

Forthyrontabletsabsorptioncanbedecreasedbyinductionofvomitingandoral

administrationofbothactivatedcharcoalandmagnesiumsulphateonce.

Overdosesofthreeuptosixtimeslabelrecommendedstartingdosefor4consecutiveweeks

inhealthy,euthyroiddogsresultedinnosignificantclinicalsignsthatcouldbeattributedto

treatment.Singleoverdoseupto3-6xtherecommendeddosedoesnotposeathreattothe

dog,andnoactionsarenecessary.However,followingchronicover-supplementation,clinical

signsofhyperthyroidismsuchaspolydipsia,polyuria,panting,weightlosswithoutanorexia,

andeitherorbothtachycardiaandnervousnessmaytheoreticallyoccur.Thepresenceof

thesesignsshouldresultinevaluationofT

serumconcentrationstoconfirmthediagnosis,

andimmediatediscontinuanceofthesupplementation.Oncethesignshaveabated(daysto

weeks),thethyroiddosagehasbeenreviewed,andtheanimalhasfullyrecovered,alower

dosagemaybeinstituted,withtheanimalbeingmonitoredclosely.

4.11.Withdrawalperiods

Notapplicable.

5. PHARMACOLOGICALPROPERTIES

Pharmacotherapeuticgroup:syntheticthyroidhormones

ATCvetcode:QH03AA01.

Revised:October2010

AN:01014/2009

5.1. Pharmacodynamicproperties

Pharmacologicallylevothyroxineisclassifiedasahormonalpreparationthatreplaces

deficientendogenoushormones.

LevothyroxineT

isconvertedtotriiodothyronineT

actsoncellularprocessesviaspecific

ligand-receptorinteractionswiththenucleus,themitochondria,andtheplasmamembrane.

InteractionofT

withbindingsitesleadstoaugmentedtranscriptionofDNAormodulationof

RNA,thusinfluencingproteinsynthesisandenzymeaction.

Thyroidhormonesactonmanydifferentcellularprocesses.Indevelopinganimalsandhuman

beings,theyarecrucialdeterminantsofnormaldevelopment,especiallyinthecentralnervous

system.Thyroidsupplementationincreasesbasalcellularmetabolismandoxygen

consumptiontherebyaffectingthefunctionofvirtuallyallorgansystems.

5.2. Pharmacokineticparticulars

SomedogsappearedtoconsistentlyeitherabsorbL-thyroxinebetterand/oreliminateitmore

slowlythandootherdogs.Furthermoreabsorptionandeliminationrateisinfluencedbydaily

intakeoflevothyroxinesodium(highabsorption/loweliminationincaseoflowintakeandvice

versaincaseofhighintake).Thevariabilityinpharmacokineticparametersbetween

individualdogsisconsiderableand,althoughthepresenceoffoodmayaffectabsorption,itis

consideredtohaveaminoreffectontheparametersoverall.Absorptionisrelativelyslowand

incomplete:InmostcasesT

occursbetween1to5hoursafteroraladministration,mean

variesmorethan3foldbetweendogsonthesamedoses.Inadequatelydoseddogs

theplasmapeakapproachesorslightlyexceedstheupperlimitofnormalplasmaT

levels,

andbytheendof12hoursafteroraladministration,plasmaT

usuallydeclinestothelower

halfofthenormalrange.TheratesofdisappearanceofT

fromtheplasmaareslowedin

hypothyroidism.Alargepartofthethyroxineistakenupbytheliver.L-thyroxineisboundto

plasma-proteinsandplasmalipoproteins.Partofadoseofthyroxineismetabolisedtothe

morepotenttriiodothyronine(T

)bydeiodination.Theprocessofdeiodinationcontinues.

Thesefurtherdeiodinatedmetabolicproducts(otherthanT

andT

)donothavethyromimetic

activity.Otherpathwaysofthyroidhormonemetabolismincludeconjugationtoformsoluble

glucuronidesandsulphatesforbiliaryorurinaryexcretionaswellascleavageoftheether

linkageoftheiodothyroninemolecule.Inthedog,over50%oftheT

producedeachdayare

lostinthefaeces.TheextrathyroidalbodystoresofT

areeliminatedandreplacedinabout1

day.

6. PHARMACEUTICALPARTICULARS

6.1. Listofexcipients

Calciumhydrogenphosphatedihydrate,

Cellulose,Microrcrystalline,

SodiumStarchGlycolate(typeA),

Magnesiumstearate.

6.2. Incompatibilities

Notapplicable

Revised:October2010

AN:01014/2009

6.3. Shelf-life

Shelf-lifeoftheveterinarymedicinalproductaspackagedforsale:2years

Tabletportionscanbekeptfor4daysintheblisterpack.

6.4. Specialprecautionsforstorage

Donotstoreabove25°C.

6.5. Natureandcontentsofimmediatepackaging

Blisters,consistingofaluminiumfoilandawhite,opaquePVC/PE/PVDCfoil.

10Tabletsperblister,5,25,or50blisterspercarton,50,250or500tabletspercarton.

Notallpacksizesmaybemarketed.

6.6. Specialprecautionsforthedisposalofunusedveterinarymedicinalproductor

wastematerials,derivedfromtheuseofsuchproductsifappropriate.

Anyunusedproductorwastematerialshouldbedisposedofinaccordancewithnational

requirements.

7. MARKETINGAUTHORISATIONHOLDER

EurovetAnimalHealthB.V.

Handelsweg25,5531AEBladel

TheNetherlands

8. MARKETINGAUTHORISATIONNUMBER

Vm16849/4005

9. DATEOFRENEWALOFTHEAUTHORISATION

13April2010

10. DATEOFREVISIONOFTHETEXT

October2010