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Flashcards in Thyroid Deck (13):
1

Hypothyrodism in dogs
-Goal of therapy
-Drugs

Replace hormone the body is not producing
Liothyronine (T3) or Levothyroxine (T4)

2

Levothroxine pharmacokinetics

Requires less frequent dosing and has lower risk of causing throtoxicois (excessive T4 levels)
Dosed in mg/kg - Reduced risk of over supplementation in large patient by doings mg/m2
Must be given for the rest of patient's life

3

How to monitor hypothyroidism in dogs

Monitor by measuring T4 levels
Start measuring 4 weeks after starting therapy
Be mindful of drugs that could interfere with thyroid test results (phenobarbital, zonisamide, sulfonamides, glucocrticoids, phenylbutazone, quinidine)

4

Only veterinary approved product for hypothyroidism in dogs

Thyro-tabs

5

Goal of therapy for cats with hyperthyroidism

Stop excessive hormone production

6

Therapy options for hyperthyroidism in cats

Surgery (thyroidectomy) = remove abnormal tissue
Radioactive iodine = remove abnormal tissue
Diet with Hill's y/d = prevent production (iodine uptake)
Pharmacologic therapies = prevent production (interfere with synthesis), prevent release of performed hormone, prevent conversion of T4 to T3

7

Pharmacologic options for Hyperthyroidism in cats

Methimazole
Propylthiouracil
Iodides/Iodinated Contrast Agents

8

Methimazole

Inhibits thyroid synthesis
Consistently efficacious
Side effects uncommon and most are manageable

9

Propylthiouracil

Inhibit thyroid synthesis
Inhibit conversion of T4 to T3 in tissues
Higher incidence of serious side effects (higher risk)

10

Iodides/Iodinated Contrast Agents

Efficacy is variable and often transient
Inhibit thyroid synthesis
Inhibit released of performed hormone
Inhibit T3 to T4 conversion in periphery

11

3 Methimazole drugs

Tapazole (human approved)
Felimazole (veterinary approved)
Transdermal methimazole (no commercial product, obtained through compounder)

12

Side effects of Methimazoles

Mild/common = GI signs (vomiting), transient hematologic changes on CBC
Severe/uncommon = refractory GI signs, idiosyncratic reactions (facial excoriation, hepatopathy, bone marrow suppression)

13

Carbimazole

Converted in the body to methimazole