Chapter 31 Thyroid and Antithyroid Flashcards
1
Q
Thyroid Augmentation Drugs
A
- Levothyroxine; Eltroxin or Synthroid ( T4 - preferred drug). Preferred drug because its hormonal content is standardized.
- Work the same way as endogenous thyroid hormones: Metabolic rate (lipid, carbs, protein); increase O2 Consumption, temp, blood volume , and cell growth; increase myocardial β receptors (increase cardiac output); increase kidney blood flow (GFR; diuretic effect)
- Never discontinue abruptly
- Give same time each day to maintain consistent blood levels
- Take in am to decrease insomnia
- DO NOT INTERCHANGE BRANDS! Brands are not equivalent in dosing
2
Q
Contraindications, adverse effects, and interactions of Thyroid Augmentation Drugs
A
- Contraindications include: MI, Adrenal insufficiency, hyperthyroidism
- Adverse Effects include: Cardiac dysrhythmia with the risk for fatal irregularities, Insomnia, tremors, headache, anxiety, Nausea diarrhea, appetite changes, cramps, Weight loss, menstrual irregularities, sweating, heat intolerance, fever
- Interactions include: Enhance warfarin so reduce dose, Reduce digoxin and insulin so increase, Increased sensitivity to epinephrine, and Cholestyramine (calcium and aluminum bind in GI tract and reduce absorption both drugs)
3
Q
Pharmacokinetics of Thyroid Augmentation Drugs
A
- Onset 2 days
- Peak 3-4 weeks
- Duration 1-3 weeks
- Half life average is 7 days (min is 3-5 days and max is 9-10 days)
- More then 99% protein bound so it stays in the body longer and increases the risk for toxicity
4
Q
Antithyroid drugs
A
- Thioamide derivatives
- Inhibits iodine which impedes thyroid hormone function
- Propylthiouracil (can also inhibit the conversion of T3 to T4)
- Used to palliate hyperthyroidism and to prevent the surge in thyroid hormones that occurs after surgical treatment or during radioactive iodine treatment for hyperthyroidism/thyroid cancer
- Adverse effects: may cause liver and bone marrow toxicity
- Interactions: increased activity with oral coagulants and Increased leukopenia with other bone marrow depressants
