E1. Thyroid drugs Flashcards Preview

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Flashcards in E1. Thyroid drugs Deck (25):

Look at slides 5 – 7, functions of the thyroid.



What is hypothyroidism?

Decrease overall production of T3/T4 by the thyroid. Usually lymphocytic thyroiditis or idiopathic atrophy of the thyroid. Rarely secondary or tertiary.


What is the goal of treating hypothyroidism?

To replace the lack of hormone production


What are the two drugs available to treat hypothyroidism? Which hormone are they related to, T3 or T4?

Levothyroxine (T4) and Liothyronine (T3)


What is the difference between levothyroxine and liothyronine, other than the one is T3 and one is T4. (onset of action, duration, potency)

– fast onset of action
– shorter half-life (6 hours)
– more potent than T4 (2 – 10x)
– *may be used in dogs with reduced ability to convert T4 to T3. As greater G.I. absorption in canines than levothyroxine.

Levothyroxine (T4):
– slower onset of action
– longer half-life (9 – 15 hours)
– less potent than T3


What is the drug of choice to treat hypothyroidism in all animals?



After how many weeks of treatment should you monitor the serum T4 levels?

4 weeks


You have a dog with hypothyroidism and G.I. issues (malabsorption) which drug should you give?
A. Levothyroxine
B. Epinephrine
C. Furosimide
D. Liothyronine
E. Let the dog die

D. Liothyronine


What are the mg typically used as oral tablets of levothyroxine sodium ? (7)t

0.1, 0.2, 0.3, 0.4, 0.6, 0.7, and 0.8.


How long is the levothyroxine sodium peak plasma concentration time? How long is the serum half-life?

Peak plasma concentrations is between 4 – 12 hours past dose.

serum half-life is 12 – 16 hours


Which is more of an issue, acute overdose or chronic overdose of levothyroxine sodium?

Chronic. Acute overdose is less of an issue than chronic.


If an overdose of levothyroxine happens, what is it called and what are the signs you are likely to see?

Thyrotoxicosis – vomiting/diarrhea, tachycardia, tachypnea, weight loss, hyperactivity, and hypertension.

*Slide 12 has drug names


What are some of the general considerations when treating hypothyroidism?

Monitoring is done by testing plasma T4 levels.

Recommended it to start patients at standard dosing:
–0.02 mg/kg PO b.i.d.
– check thyroid levels after four weeks
– adjust dose based on T4 level and clinical signs

Not all formulations are equal.

*look at slide 13 for more considerations


What is myxedema?

What is myxedema coma? How do you go about treating it?

Accumulation of mucopolysaccharides and hyaluronic acid in the dermis or even around the peripheral nerves.

Rare manifestation of hypothyroidism in the brain and is a medical emergency You treat with levothyroxine sodium for injection (IV?), warm the patient, respiratory support, and fluid/electrolyte support.


What are the drugs that interfere with thyroid testing? (8)



Look at slide 18, talks about hyperthyroidism causes.



Which of the below are good options to treat hyperthyroidism (in Dr. Boots opinion)?
A. Surgical thyroidectomy
B. Diet (Hills Y/D)
C. Anti-thyroid drugs
D. Intra-thyroid injection of ethanol
E. Radioactive iodine (I – 131)

B, C, E.


What is considered to be the gold standard of hyperthyroid treatment?

Radioactive iodine therapy


How does radioactive iodine therapy work on treating hyperthyroidism?

It emits beta particles that will selectively destroy thyroid tissue.


How long it is radioactive iodine therapies half-life?

Eight days


Look at slide 20(Slide 5 in tutor slides) more info on radioactive iodine therapy.



Look at slide 21-22 (slide 6-8 tutor slides) for drugs to treat hyperthyroidism.



What is the anti-thyroid drug of choice for treatment in hyperthyroidism?



What are some of Methimazoles side effects?

Vomiting/anorexia (10%), transient/mild hematology changes (15%), acquired myasthenia gravis (unicorn)
*look at slide 23 for more side effects


Look at slide 24 – 28 (slide 9 – 11 tutors slides).