Endocrine Medications: Thyroid Flashcards
1
Q
What are thyroid drugs?
A
Contain:
- T3
- T4
- Or a combo of both T3 and T4
2
Q
Are thyroid drugs natural or synthetic?
A
They can be either
3
Q
What are natural thyroid drugs are made from?
A
animal thyroid
4
Q
What does natural thyroid contain?
A
thyroid USP
thyroglobulin
5
Q
What do thyroid USP and thyroglobulin contain?
A
- T3
2. T4
6
Q
What are synthetic thyroid drugs are made from?
A
Sodium salts of the L-isomers of the hormones
7
Q
What are the different synthetic hormones?
A
- levothyroxine sodium (T4)
- Liothyronine sodium (T3)
- liotrix (T3 and T4)
8
Q
How fast are thyroid hormones absorbed?
A
Variably
9
Q
Where are thyroid hormones absorbed?
A
GI tract
10
Q
Where are thyroid hormones distributed?
A
- Plasma
2. Bound to serum proteins
11
Q
By what method are thyroid hormones metabolized?
A
Deiodination
12
Q
Where are thyroid hormones metabolized?
A
In the liver
13
Q
How are thyroid hormones excreted?
A
In feces
14
Q
Are thyroid hormones excreted changed or unchanged?
A
Unchanged
15
Q
What is the effect of thyroid hormones on the body?
A
An increased metabolic rate in body tissues
16
Q
How to thyroid hormones increase metabolic rate in body tissues?
A
- Affect protein and carb metabolism
- Stimulate protein synthesis
- Promote gluconeogenesis
- Increase the use of glycogen stores
17
Q
What do thyroid hormones increase?
A
- Metabolic rate
- HR
- Cardiac output
18
Q
What is cardiac output?
A
The amount of blood pumped by the heart each minute)
19
Q
It is POSSIBLE that thyroid hormones ALSO increase what?
A
- Heart’s sensitivity to catecholamines
2. The number of beta-adrenergic receptors in the heart
20
Q
What is the result of the stimulation of beta receptors in the heart?
A
Increases heart rate and contractility
21
Q
Since thyroid hormones increase blood flow what other system becomes effected?
A
Renal
22
Q
How do thyroid hormones effect the renal system?
A
- Increase the glomerular filtration rate
2. Which causes diuresis
23
Q
What is glomerular filtration rate?
A
The amount of plasma filtered
through the kidneys each minute
24
Q
What is the Brand name of Levothyroxine?
A
Synthroid
25
What is the main action of Levothyroxine?
1. Stimulates metabolism of all body tissues
2. By accelerating the rate of
cellular oxidation
26
For what conditions is Levothyroxine indicated?
1. Cretinism
2. Myxedema coma
3. Thyroid hormone replacement
27
What are the adverse effects of Levothyroxine?
1. Nervousness
2. Insomnia
3. Tremor
4. Tachycardia
5. Palpitations
6. Angina
7. Arrhythmias
8. Cardiac arrest
28
What is important to remember when writing prescriptions for levothyroxine? Why is it important to remember this?
1. The unit of measurement
| 2. Medication error can occur is written in incorrect unit
29
In what unit of measurement is Levothyroxine prescribed?
Mcg
30
In which patents should Levothyroxine be used with extreme caution?
1. Elderly
| 2. CV disorders
31
In what situations are thyroid drugs used as replacement hormones?
1. to treat many forms of hypothyroidism
2. Taken with antithyroid drugs to prevent goiter formation (an enlarged
thyroid gland) and hypothyroidism
3. to differentiate between primary and secondary hypothyroidism during diagnostic testing
4. to treat papillary or follicular thyroid carcinoma.
32
What is thyroid-stimulating hormone?
TSH
33
What is the drug of choice for thyroid-stimulating hormone (TSH) suppression therapy?
Levothyroxine
34
What common drugs do thyroid drugs interact with?
1. Oral anticoagulants
2. Cholestyramine
3. Colestipol
4. Phenytoin
5. Digoxin
6. Carbamazepine
7. Phenobarbital
8. Rifampin
9. Theophylline
35
How do anticoagulants interact with thyroid drugs?
1. They increase the effects
| 2. Increased tendency to bleed
36
How does Cholestyramine interact with thyroid drugs?
Reduces the absorption of thyroid
37
How does Colestipol interact with thyroid drugs?
Reduces the absorption of thyroid
38
How does Phenytoin interact with thyroid drugs?
May accelerate metabolism of levothyroxine
39
How does Digoxin interact with thyroid drugs?
1. May reduce serum digoxin levels
| 2. Which can increase risk of arrhythmias or HF
40
How does Carbamazepine interact with thyroid drugs?
1. Increases thyroid hormone metabolism 2. Which reduces the effectiveness
41
How does Carbamazepine interact with thyroid drugs?
1. Increases thyroid hormone metabolism 2. Which reduces the effectiveness
42
How does phenobarbital interact with thyroid drugs?
1. Increases thyroid hormone metabolism 2. Which reduces the effectiveness
43
How does rifampin interact with thyroid drugs?
1. Increases thyroid hormone metabolism 2. Which reduces the effectiveness
44
How does theophylline interact with thyroid drugs?
Serum theophylline levels may increase
45
What causes most adverse reactions to thyroid drugs?
Toxicity
46
What systems do the adverse reactions of thyroid drugs effect?
1. GI
2. Cardiac
3. General Systemic
47
What are the adverse reactions of thyroid drugs that occur in the GI system?
1. Diarrhea
2. Abdominal cramps
3. Weight loss
4. Increased appetite
48
What are the adverse reactions of thyroid drugs that occur in the Cardiac system?
1. Palpitations
2. Sweating
3. Rapid HR
4. Increased BP
5. Angina
6. Arrhythmias
49
What are the adverse reactions of thyroid drugs that occur in generally?
1. Headache
2. Tremor
3. Insomnia
4. Nervousness
5. Fever
6. Heat intolerance
7. Menstrual irregularities
50
What should be monitored in patients undergoing treatment with thyroid drugs? When should this occur?
1. HR/BP: Regularly
2. Signs of thyrotoxicosis (inadequate dosage): Regularly
3. PT/INR: Regularly
4. Thyroid function test results: Regularly
5. T4: Normal levels should occur within 24 hours
6. T3: Three fold increase in levels in 3 days
51
When prescribing thyroid hormones what is important to remember about dosages? What action may be indicated?
1. Dosages vary widely
2. Begin treatment at lowest level
3. Adjust to higher doses according to the patient’s symptoms and laboratory data
52
What time of the day and at what frequency should thyroid hormones be taken?
1. Same time each day (once)
| 2. In the AM
53
Why is it recommended that thyroid hormones are to be take in the AM
To prevent insomnia
54
Which patients have special considerations to consider when undergoing treatment with thyroid drugs?
1. CAD
2. Taking anticoagulants
3. Switching from levothyroxine to liothyronine
4. Switching from liothyronine to levothyroxine
5. Needs radioactive iodine uptake studies
6. DM
55
What are the special considerations to consider when a patient with CAD is undergoing treatment with thyroid drugs?
Monitor for occurrence of coronary artery insufficiency
56
What are the special considerations to consider when a patient taking anticoagulants is undergoing treatment with thyroid drugs?
1. Monitor PT/INR
| 2. Dose may need to be lowered
57
What are the special considerations to consider when a patient is switching from levothyroxine to liothyronine?
1. Start levothyroxine several days before withdrawing liothyronine
2. To avoid relapse.
58
What are the special considerations to consider when a patient is switching from liothyronine to levothyroxine?
1. Start levothyroxine several days before withdrawing liothyronine
2. To avoid relapse.
59
What are the special considerations to consider when a patient needs radioactive iodine uptake studies and is undergoing treatment with thyroid drugs? Why?
1. Must d/c the drug 4 weeks before the test
| 2. Thyroid hormones alter thyroid function test results
60
What are the special considerations to consider when a patient with DM is undergoing treatment with thyroid drugs?
May need an increased antidiabetic dosage when starting
61
Is it okay to stop thyroid medications? how long should patients be taking thyroid hormones?
1. Do not stop abruptly
| 2. Therapy is usually lifelong
