Download Drugs used in hypothyroidism

DRUGS USED IN
HYPOTHYROIDISM
by
Dr.Abdul latif Mahesar
Objectives
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At the end of the lecture the students will be able
to :
Classify common drugs used for treatment of
hypothyroidism
Details the drugs regarding , mechanism of
action , pharmacological effects , clinical uses &
side effects
Recognize treatment of special cases of
hypothyroidism .
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Hypothyroidism
Thyroid gland does not produce enough
hormones
 CAUSES
 Congenital ( cretinism , dwarfism)
 Autoimmune disorder ( Hashimotos
thyroiditis)
 Irradiation
 Surgical removal of thyroid gland
 Thyroid carcinoma
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CAUSES
Congenital which results to ( cretinism ,
dwarfism)
 Autoimmune disorder ( Hashimotos
thyroiditis)
 Irradiation Of the gland
 Surgical removal of thyroid gland
 Thyroid carcinoma
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HYPOTHYROIDISM

People who are most at risk include those over age 50
& mainly in females
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Diagnosed by low plasma levels of T3 & T4
and high levels of TSH.
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Manifestations of Hypothyroidism
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Fatigue and lack of energy
weight gain
Dry and cold skin
Dry hairs
Constipation
Slowed thinking
Bradycardia
Heavy menses
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Treatment
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Replacement therapy with synthetic thyroid
hormone preparations
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Thyroid preparations
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LEVOTHYROXINE: (T4)
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A synthetic form of the thyroxine (T4) , is the drug of
choice for replacement therapy .
Stable and has a long half life ( 7 days) .
Administered once daily.
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Oral preparations available from 0.025 to 0.3 mg
tablets
Absorption is increased when hormone is given on empty
stomach
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Parentral preparation 200-500µg .
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In old patients and in patients with cardiac
problems , treatment is started with reduced
dosage.
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Normal thyroid levels are restored within 2-3
weeks.
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levothyroxine(T4) is given in a dose of 12.5 – 25
µg/day for two weeks and then increasing it after
every two weeks.
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Clinical uses
Hypothyroidism, regardless of etiology
including :

Congenital

Autoimmune thyroiditis ( Hashimoto
thyroiditis)

Pregnancy

Thyroid carcinoma
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ADVERSE EFFECTS OF OVER DOSES
CHILDREN : Restlessness, insomnia,
accelerated bone maturation.
ADULTS :
Tachycardia, palpitation, cardiac
arrhythmias, tremor , restlessness , heat
intolerance , headache, muscle pain
Change in appetite, diarrhea, weight loss
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Adverse effects of under-dosing
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Sluggishness
Mental dullness
Feeling cold
Muscle cramps
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Liothyronine(T3)
More potent (3-4 times) and rapid action than
levothyroxine but has a short half life is not
recommended for routine replacement
therapy, it requires multiple daily doses.
 It should be avoided in cardiac patients.
 It is best used for short –term suppression of
TSH.
 Oral preparation available are 5-50µg tablets
 Parentral use 10µg/ml
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MYXEDEMA COMA:
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Life –threatening hypothyroidism
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The treatment of choice is loading dose of levothyroxine
intravenously 300-400µg initially followed by 50µg daily.
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I.V liothyronine for rapid response but it may provoke
cardiotoxicity
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I.V hydrocortisone may be used in case of adrenal and
pituitary insufficiency.
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HYPOTHROIDSM AND PREGNANCY.
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In pregnant hypothyroid patient 20-30 %
increase in thyroxine is required because of
elevated maternal TBG(thyroxine binding
globulin) induced by estrogen and
because of early development of fetal brain
which depends on maternal thyroxine
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Combination drugs
LIOTRIX
is a combination of synthetic T4 and
T3 in a ratio of 4:1 that attempt to mimic the
natural hormone secretions
Major limitation to this product are high cost
And lack of therapeutic rationale,because about
35% of T4 is peripherally converted to T3.
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