DRUGS USED IN DRUGS USED IN HYPOTHYROIDISMHYPOTHYROIDISM

Objectives Objectives

At the end of the lecture the students At the end of the lecture the students will be able to :will be able to :

Classify common drugs used for Classify common drugs used for treatment of hypothyroidism treatment of hypothyroidism

Details the drugs regarding , Details the drugs regarding , mechanism of action , mechanism of action , pharmacological effects , clinical pharmacological effects , clinical uses & side effects uses & side effects

Recognize treatment of special cases Recognize treatment of special cases of hypothyroidism .of hypothyroidism . 2

HypothyroidismHypothyroidism

Thyroid gland does not produce Thyroid gland does not produce enough hormonesenough hormones

CongenitalCongenital ( ( cretinism , dwarfismcretinism , dwarfism)) Autoimmune disorder Autoimmune disorder

( ( Hashimotos thyroiditis)Hashimotos thyroiditis) IrradiationIrradiation Surgical removal Surgical removal of thyroid glandof thyroid gland Thyroid carcinoma Thyroid carcinoma

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HYPOTHYROIDISMHYPOTHYROIDISM People who are most at risk include those People who are most at risk include those over age 50 over age 50

& mainly in & mainly in femalesfemales

Diagnosed by low plasma levels of T3 & T4Diagnosed by low plasma levels of T3 & T4

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Manifestations of Manifestations of HypothyroidismHypothyroidism

Fatigue and lack of energyFatigue and lack of energy weight gainweight gain Dry and cold skin Dry and cold skin Dry hairsDry hairs ConstipationConstipation Slowed thinkingSlowed thinking BradycardiaBradycardia Heavy mensesHeavy menses

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TreatmentTreatment

Replacement therapy with Replacement therapy with synthetic thyroid hormone synthetic thyroid hormone preparationspreparations

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Thyroid preparationsThyroid preparations LEVOTHYROXINE: (TLEVOTHYROXINE: (T44))

A synthetic form of the thyroxine (TA synthetic form of the thyroxine (T44) , is the drug of ) , is the drug of choice for replacement therapy .choice for replacement therapy .

Stable and has a long half life ( 7 days) .Stable and has a long half life ( 7 days) . Administered once daily.Administered once daily.

Oral preparations Oral preparations available from 0.025 to 0.3 mg available from 0.025 to 0.3 mg tabletstabletsAbsorption is increased when hormone is given on Absorption is increased when hormone is given on empty empty

stomachstomach

ParnteralParnteral preparation 200-500µg . preparation 200-500µg .

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IIn n old patients old patients and in patients with and in patients with cardiac cardiac problems , treatment is started problems , treatment is started with reduced dosage.with reduced dosage.

Restore normal thyroid levels within 2-Restore normal thyroid levels within 2-3 weeks.3 weeks.

levothyroxine is given in a dose of levothyroxine is given in a dose of 12.5 – 25 µg/day for two weeks and then 12.5 – 25 µg/day for two weeks and then increasing it after every two weeks.increasing it after every two weeks.

Clinical uses Clinical uses

Hypothyroidism, regardless of Hypothyroidism, regardless of etiology including :etiology including :

congenitalcongenital Autoimmune thyroiditis Autoimmune thyroiditis

( Hashimoto ( Hashimoto thyroiditis)thyroiditis)

Pregnancy Pregnancy Thyroid carcinoma Thyroid carcinoma

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ADVERSE EFFECTS OF ADVERSE EFFECTS OF OVER DOSESOVER DOSES CHILDRENCHILDREN : : Restlessness, Restlessness,

insomnia, accelerated bone maturation.insomnia, accelerated bone maturation. ADULTS :ADULTS :

Tachycardia, palpitation, cardiac Tachycardia, palpitation, cardiac arrhythmias, tremor , restlessness , arrhythmias, tremor , restlessness , heat intolerance , headache, muscle heat intolerance , headache, muscle pain pain

Change in appetite, diarrhea, Change in appetite, diarrhea, weight loss weight loss

Adverse effects of under-Adverse effects of under-dosingdosing

SluggishnessSluggishness Mental dullnessMental dullness Feeling coldFeeling cold Muscle crampsMuscle cramps

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Liothyronine(TLiothyronine(T33))

More potent More potent (3-4 times) and (3-4 times) and rapid action than rapid action than levothyroxine but has a levothyroxine but has a short half life short half life is not is not recommended for routine replacement recommended for routine replacement therapy, it requires multiple daily doses.therapy, it requires multiple daily doses.

It should be It should be avoidedavoided in cardiac patients. in cardiac patients. It is best used for short –term therapy.It is best used for short –term therapy. Oral preparation Oral preparation available are 5-50µg tabletsavailable are 5-50µg tablets ParnteralParnteral use 10µg/ml use 10µg/ml

LIOTRIXLIOTRIX

Combination of syntheticT4 & T3 Combination of syntheticT4 & T3 in a ratio 4:1 that attempt to in a ratio 4:1 that attempt to mimic the natural hormonal mimic the natural hormonal secretion.secretion.

The major limitations to this The major limitations to this product are high cost & lack of product are high cost & lack of therapeutic rationale because therapeutic rationale because 35% of T4 is peripherally 35% of T4 is peripherally converted to T3converted to T3

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MYXEDEMA COMA:MYXEDEMA COMA: Life –threatening hypothyroidism Life –threatening hypothyroidism

The treatment of choice is loading dose of The treatment of choice is loading dose of levothyroxine levothyroxine intravenouslyintravenously 300-400µg initially followed by 50µg daily. 300-400µg initially followed by 50µg daily.

I.V I.V liothyronineliothyronine for for rapid response rapid response but it may provoke but it may provoke cardiotoxicitycardiotoxicity

I.V I.V hydrocortisonehydrocortisone may be used in case of adren may be used in case of adrenal and al and pituitary insufficiency.pituitary insufficiency.

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HYPOTHROIDSM AND PREGNANCYHYPOTHROIDSM AND PREGNANCY..

In pregnant hypothyroid patient 20-30 % In pregnant hypothyroid patient 20-30 % increase in thyroxine is required because of increase in thyroxine is required because of elevated maternal TBG induced by estrogen elevated maternal TBG induced by estrogen andand

because of early development of fetal brain because of early development of fetal brain which depends on maternal thyroxinewhich depends on maternal thyroxine