CC Jan 2016 Thyroid medications

echoecho's version from 2016-01-05 14:02


Question Answer
Why is an accurate medication list essential in patients taking Levothyroxine?1) many patients treated with levothyroxine (Synthroid) for hypothyroidism take medications that have the potential to interfere with levothyroxine absorption or metabolism 2) other medications may also interfere with the secretion of TSH, making it difficult to accurately interpret the effectiveness of levothyroxine replacement
List the medications that may inhibit normal secretion of TSH? What is the sequelae?1) high-dose corticosteroids 2) dobutamine (Dobutrex) 3) dopamine (>1 mcg/kg/min) 4) levodopa (Sinemet) 5) octreotide (Sandostatin) 6) in those taking levothyroxine, this may result in a low level of TSH despite an adequate dose of their thyroid replacement product
Comment on what Metformin (Glucophage) has on TSH secretion?it is also associated with suppression of normal TSH secretion through an unclear mechanism
Comment on metoclopramide (Reglan) on its effect on TSH secretion?it can increase TSH secretion
Some meds alter thyroxine-binding globulin (TBG) level. In euthyroid patients not requiring thyroid replacement, increases or decreases in TBG cause a parallel change in total ____ and total ____ but do NOT affect metabolically active _____ ____ and ____ _____ levels?T3; T4; free T3; free T4
Some meds alter thyroxine-binding globulin (TBG) level. In patients taking thyroid replacement, they CANNOT compensate for changes in TBG as well so that ____ ____ and _____ ______ levels change?free T4; free T3
In patients taking Levothyroxine, medications that lower serum TBG (thyroxine-binding globulin), will ______ (decrease vs. increase) the levels of free T4 and free T3? List medications examples?1) increase 2) androgens, anabolic steroids, glucocorticoids
Drugs that raise the TBG levels result in ______ (lower vs. higher) levels of free T4 and free T3. List medication examples?1) lower 2) estrogens (including oral contraceptives), selective estrogen receptor modulators (Tamoxifen [Nolvadex], raloxifene [Evista]), methadone (Dolphine), fluorouracil
As one example, TBG increases will stabilize _____ weeks after initiating estrogen therapy so it would be prudent for providers to recheck thyroid function _____ months after adding estrogen therapy for patients already taking levothyroxine?12; 3
Give samples of medications that BLOCK the binding of thyroid hormone to TBG, thus lowering the serum levels of total T4 and total T3? 1) Salicylates > 2 g/day 2) salsalate (Disalcid) > 3 g/day 3) IV furosemide (Lasix) > 80 mg/day
Subcutaneous heparin administration may transiently INCREASE serum free T4 due to what?displacement of T4 from TBG. This effect is generally not clinically significant.
*** Diseases or medications (PPIs) that decrease gastric acid may also ______ (decrease vs. increase) levothyroxine absorption?decrease
Therefore, since thyroxine requirements may increase with PPI therapy, what testing should be done after initiation of PPI therapy?thyroid function testing
List 3 diseases that can affect levothyroxine availability due to malabsorption?1) celiac disease 2) H. pylori gastritis 3) diabetic gastroparesis
List an example of a drug that interfers with the absorption of Levothyroxine from the GI tract? Because of this when should Levothyroxine be given?1) cholestyramine (Questran) bind Levothyroxine and inhibits its absorption 2) at least 6 hours should separate taking Levothyroxine from cholestyramine (Questran)
Comment on simultaneous use of calcium carbonate and levothyroxine on free T4 levels and TSH? Do levels of TSH and free T4 return to normal when calcium is no longer taken at the same time?1) lowers free T4 levels 2) raises TSH 3) yes
Mean TSH levels increase > ___ mU/L with calcium use?1
List other medications that decrease Levothyroxine absorption?1) raloxifene 2) sucralfate (Carafate) 3) ferrous sulfate 4) aluminum hydroxide
List medications that may INCREASE thyroid hormone metabolism, and any patient starting these meds may need HIGHER doses of Levothyroxine to regain an euthyroid state?1) phenobarbital 2) rifampin (Rifadin) 3) phenytoin (Dilantin) 4) carbamazepine (Tegretol) 5) sertraline (Zoloft)
Patients with nephrotic syndrome may sometimes require ______ Levothyroxine dose?increased
*** Food can impair Levothyroxine absorption. The best Levothyroxine absorption occurs when the patient is in what state? What are the recommendations as to when to take Levothyroxine?1) fasting 2) dosing of Levothyroxine 1 hour BEFORE breakfast
The fasting state is more important than what?the time of administration (morning vs. evening), however, most patients find it easier to be fasting in the morning before breakfast rather than in the evening
List 6 examples of dietary intake that may interfere with levothyroxine absorption?1) soy protein 2) walnuts 3) grapes 4) papaya 5) coffee 6) high levels of dietary fiber
*** SUMMARY = Medications can inhibit or increase ____ secretion?TSH
*** SUMMARY = Medications that affect _______ can affect circulating thyroid hormone levels?TBG (thyroxine-binding globulin)
*** SUMMARY = Medications or diseases that _____ (increase vs. decrease) gastric acid _______ (increases vs. decrease) levothyroxine absorption?decrease; decrease
*** SUMMARY = The best absorption of Levothyroxine occurs when the patient is ______?fasting