Pharma L2 Thyroid & Antithyroid Drugs Flashcards

1
Q

Which drugs accelerate breakdown of thyroid hormones ?

A

Phenytoin, phenobarbital, rifampin

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2
Q

Which drugs cause primary hypothyroidism ?

A

Carbimazol, propyl-thyrouracil

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3
Q

Liothyronin (T3) & Levothyroxine (T4) PKs

A

1) TSH levels determine improvement
2) Levothyroxine stronger binding to plasma proteins—> long duration with slow onset
3) Drug if choice is Levothyroxine

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4
Q

Levothyroxine Food & drug interactions

A

1) Given on empty stomach (soybeans & walnuts decrease absorption)
2) 2-4 hrs before or after calcium or iron supplements (since they reduce absorption)

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5
Q

Enzyme inhibitors

A

1) Grapefruit
2) Cimetidine
3) ketoconazol
4) Erythromycin
5) ciprofloxacin
6) omeprazol

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6
Q

Enzyme inducers

A

Alcohol, phenobarbital, carbamazepine, rifampin, phenytoin

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7
Q

Which drugs decrease synthesis of hormones?

A

Thioamides: Carbimazole, propyl-thiouracil, methimazole

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8
Q

Thioamines MOA

A

1) inhibit TPO (inhibits Iodide ion oxidation to iodine)
2) inhibit Coupling
3) PTU inhibits peripheral deiodinase

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9
Q

Onset of Thioamines and why?

A

Delayed & slow because no effect on stored thyroglobulin

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10
Q

Which of the thioamines is teratogenic and which isn’t?

A

Methimazole (long HL) is teratogenic while PTU is not (Short HL highly ionized in blood)

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11
Q

What is the active form of carbimazole?

A

Methimazole

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12
Q

Thioamines S/E

A

Agranulocytosis (granulocyte deficiency), hepatotoxicity

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13
Q

Drug of choice in treating Hyperthyroidism ?

A

Methimazole

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14
Q

MOA of iodide (Lugol’s solution)

A

1) Inhibit T3 & T4 protease enzyme preventing its release from thyroglobulin
2) transient inhibition of iodination
3) reduce size and blood supply to the gland

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15
Q

Therapeutic use of Lugol’s solution

A

Not used as solo, used in thyroid storm and before surgery

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16
Q

Thyroidectomy and I-131 treatment

A

Oral I-131 is given and is selectively taken by follicular cells
Most become hypothyroidic and require Levothyroxine

17
Q

Preparation for surgical thyroidectomy

A

1) Antithyroid drugs 1-2 months prior
2) Iodide 7-10 days prior (reduce size and vasculation)
3) propranolol 40 mg

18
Q

Thyroid storm treatment

A

Iodide (fast effect), PTU to prevent deiodination, propranolol (decrease symp. Stimulation), Hydrocortisone (🤷‍♂️)

19
Q

Order of drugs administration during thyroid storm

A

1: propranolol
2: PTU (better) / methimazol
3: iodide
4: steroids