2. CHAPTERS
• CHAPTER I : INTRODUCTION
• CHAPTER II : DEFINITION
• CHAPTER III : CLASSIFICATION OF ANTI-THYROID
• CHAPTER IV : MECHANISM OFACTION
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3. I. INTRODUCTION
• Basically thyroid disease can be classified into 2 types
1. Hypothyroidism
2. Hyperthyroidism
HYPO-THYROIDISM: It is a condition in which the thyroid glands don’t produce
enough hormones.
HYPER-THYROIDISM: It is a condition in which the thyroid gland produces excess hormones.
(use of antithyroid drugs)
CHAPTER I : INTRODUCTION
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4. II. DEFINITION
What are antithyroid agents?
These drugs are used to treat hyperthyroidism to reduce the excessive thyroid activity before
surgery and to treat and maintain patients not having surgery.
That is to lower and maintain the increased level of T3 and T4 in blood.
CHAPTER II: DEFINITION
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5. III. CLASSIFICATION OFANTI-THYROID
INHIBIT
HORMONES
SYNTHESIS
• PROPYLTHIOURACIL
• CARBIMAZOLE
• METHIMAZOLE
INHIBIT
IODIDE
TRAPPING
{IONIC
INHIBITORS}
• THIOCYNATE [-SCN]
• PERCHLORATES (-Clo4)
• NITRATES {-NO3)
INHIBIT
HORMONE
RELEASE
• IODINE
• IODIDES OF
SODIUM
• POTASSIUM
• ORGANIC IODIDE
DESTROY
THYROID
TISSUE
• RADIO ACTIVE
IODINE
ANTITHYROID
CHAPTER III : CLASSIFCATION OF ANTI-THYROID DRUGS
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6. IV. MECHANISM OF ACTION
• Drugs used:
1. Propylthiouracil
2. Carbimazole / methimazole
• MECHANISM OF ACTION
1. INHIBIT PEROXIDASE ACTION
Thyroid cell
• In thyroid cells, there is the presence of peroxidase which converts iodide into iodine. These
drugs inhibit the action of peroxidase.
• Carbimazole after metabolism gets converted into active metabolite i.e. methimazole.
• Both propylthiouracil and carbimazole inhibit the action of peroxidase which
stops the conversion.
• As we know that iodine is important for the conversion so the process stops here itself.
CHAPTER IV : MECHANISM OF ACTION
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PEROXIDASE
H2O2 I+
I-
1. INHIBIT HORMONES SYNTHESIS
7. • 2. INHIBITION OF COUPLING PROCESS
• Thyroglobulin contains tyrosine bases
• We know that, if tyrosine base contains 2 Iodine it is
known as DIT, and if contains 1 Iodine then
it is called MIT.
• If DIT combines with MIT, T3 is formed And if DIT
combines with DIT, T4 is formed
• The above process is known as coupling.
• And this drug inhibits the coupling process. therefore,
results in the inhibition of the synthesis of
thyroid hormones
Thyroid cell : thyroglobulin binds with DIT and MIT
CHAPTER IV : MECHANISM OF ACTION
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8. 3. INHIBITION DEIODINATION OF T4
• Drug used is only propylthiouracil
• T3 is more potent than T4, therefore T4
is gets converted into T3 by the process
of deiodination.
• Propylthiouracil inhibits deiodination,
which falls level of T3.
Target cell
CHAPTER IV : MECHANISM OF ACTION
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T3
T3
T3
T4
T3
T3
DEIODINATION
9. PROPYLTHIOURACIL MTHIMAZOLE /
CARBIMAZOLE
PLASMA HALF LIFE 1-2 HOURS 8 HOURS
EFFECT OF SINGLE DOSE
LAST
8 HOURS (2-3 DOSE / DAY) ENTIRE DAY (1DOSE / DAY)
USES HYPERTHYRODISM:- GRAVES DISEASE, GOITER
ADVERSE EFFECTS OF
THIOAMIDES
HYPOTHYRODISM AND GOITRE can occur due to over
treatment
CHAPTER IV : MECHANISM OF ACTION
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10. 2.INHIBIT IODIDE TRAPPING ( IONIC INHIBITORS)
Drug used : THIOCYNATE [-SCN],
PERCHLORATES(-Clo4), NITRATES(-No3)
MECHANISM OF ACTION
• The main component required from the blood
vessel is Iodide which enters into the follicle by a
symporter known as Sodium Iodide symporter
(SOD-IODIDE Symporter)
• The above drugs block SOD-IODIDE symporters,
therefore the Iodide can not enter the follicle and
the process is stopped here itself
BLOOD
VESSELS
FOLLICLE
SYMPORTER
CHAPTER IV : MECHANISM OF ACTION
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11. THIOCYNATE [-SCN] PERCHLORATES(-Clo4)
ADVERSE EFFECT • Kidney Toxicity
• Liver Toxicity
• Bone Marrow Toxicity
• Brain Toxicity
• Produce Rashes
• Fever
• Aplastic Anemia ( body stop
producing new blood cells)
• Agranulocytosis ( Lower WBC)
Clinically not used
CHAPTER IV : MECHANISM OF ACTION
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12. 3.INHIBIT HORMONE RELEASE
Drug used: Iodine, Iodides of sod,
potassium, org iodide
MECHANISM OF ACTION
• Excess amount of iodine blocks transport
of itself, that is it blocks sodium
iodine symporters.
• It also blocks by thyroid constipation
Blood vessel follicle
CHAPTER IV : MECHANISM OF ACTION
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13. IODINE IODIDES OF SOD,POTASSIUM,ORG IODIDE
ACUTE ADVERSE
EFFECT
• Swelling of lips and eyelids
• Fever
• Joint pain
• Deficiency of platelets
CHRONIC
ADVERSE EFFECT
• Inflammation of mucous membrane
• Salivation
• Sneezing
• GI disturbance
CHAPTER IV : MECHANISM OF ACTION
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14. 4.DESTROY THYROID TISSUE
• Drug use : Radio active Iodine
• MECHANISM OF ACTION
• The thyroid gland is bombarded
with Radioactive iodine which
results in destroy of thyroid cells.
• As the cells are damaged now
they can’t perform their function
i.e. they can’t produce T3 and T4
bombarding of Radioactive
isotope
( radioactive Iodine)
Thyroid Gland Destroy of
Thyroid cells
CHAPTER IV : MECHANISM OF ACTION
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15. ADVANTAGES DISADVANTAGES
• Simple
• Inexpensive
• No surgical risk
• One hyperthyroidism is controlled,
cure is permanent
• Nausea
• Loss of taste and taste change
• Swollen salivary gland
CHAPTER IV : MECHANISM OF ACTION
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