Term
| What are the four drugs to know for the treatment of HYPOthyroidism? |
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Definition
Thyroid USP
Levothyroxine sodium T4*
Liothyronine sodium T3*
Liotrix |
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Term
| What drug for hypothyroidism is a natural thyroid extract? What drugs are synthetic thyroid hormones? |
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Definition
Natural: Thyroid USP (Armour)
Synthetic:
Levothyroxine sodium T4*
Liothyronine sodium T3*
Liotrix |
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Term
| What is Thyroid USP (Armour) seldom used? |
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Definition
Absorption and bioavailability are unpredicatalbe
Unpredicatable T4
Hypersensitivity reactions because of foreign antigens |
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Term
| What is the PREFERRED replacement therapy for hypothyroidism? Why is it preferred? |
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Definition
Levothyroxine sodium T4*
Because of its consistent potency and prolonged duration of action (relatively long half-life of 8-9 days) |
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Term
| What is the metabolism of Levothyroxine sodium T4* like? |
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Definition
| Metabolized by CYP3A4 enzymes; Drugs that induce CYP450 system e.g. phenytoin, rifampin, phenobarbital increase T4 metabolism and biliary excretion |
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Term
| Adverse effects of Levothyroxine sodium T4*? |
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Definition
Tachycardia (use with caution in patients with cardiovascular problems)
Heat intolerance
Tremors
(basically signs/symptoms of hyperthyroidism)
In less severe overdoses, there is increased bone resorption leading to osteoporosis |
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Term
| How is Levothyroxine sodium T4* dosed to somebody with long-standing hypothyroidism? |
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Definition
| Correct replacement dose is a compromise between preventing myxedemic coma and cardiotoxicity |
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Term
| How are pregnant women dosed with Levothyroxine sodium T4*? |
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Definition
| Most pregnant hypothyroid patients require a 45% increase in T4 dose to ensure euthyroidism. Doses are adjusted after delivery. |
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Term
| What drug used for hypothyroidism is the DOC for myxedemic coma? |
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Definition
| Liothyronine sodium T3* (IV) |
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Term
| Adverse effects of Liothyronine sodium T3*? |
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Definition
| Similar to Levothyroxine, but Liothyronine is MORE cardiotoxic. |
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Term
| What else can Liothyronine sodium T3 be used for? |
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Definition
| Can also be used in patients who lack the ability to convert T4 to T3 |
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Term
| How does the onset of action of Liothyronine sodium T3 compare to that of |
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Definition
| It has a much faster onset of action, shorter half life, (and half the dose of T4 is needed) |
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Term
| What is the last (and currently not preferred) drug to know to treat hypothyroidism? |
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Definition
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Term
| What is the composition of Liotrix? |
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Definition
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Term
| What two classes and one single drug are used in the treatment of HYPERthyroidism? |
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Definition
Thionamides
Iodide compounds
Propranolol |
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Term
| What are the thionamide drugs to know for treating hyperthyroidism? |
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Definition
Propylthiouracil*
Methimazole* |
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Term
| What is the purpose of Propranalol in the treatment of hyperthyroidism? |
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Definition
| Propranolol is a beta-blocker that is used to inhibit 5' deiodinase in the peripheral tissue. This blocks the conversion of T4 to T3 (T3 is active form) |
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Term
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Definition
| They block thyroid peroxidase (TPO), thereby stopping the iodination and coupling of the thyroglobulin molecule. Therefore, MIT and DIT cannot be produced. Without MIT and DIT, it is impossible to produce T3 and T4. |
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Term
| What differentiates Propylthiouracil* from Methimazole*? |
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Definition
| Propylthiouracil*, like Propranolol inhibits 5' deiodinase in the peripheral tissue. This blocks the conversion of T4 to T3 (T3 is active form) |
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Term
| Adverse effects of Propylthiouracil* from Methimazole*? |
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Definition
Agranulocytosis (rare, but more important effect to watch for)
Skin rash (common) (sometime anti-histamine are give if mild symptoms)
Aplastic anemia |
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Term
| What adverse effect is only seen with Propylthiouracil*? |
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Definition
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Term
| How are Propylthiouracil* and Methimazole* used in pregnancy? |
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Definition
Both drugs cross the placental barrier, but Propylthiouracil* is safer in pregnancy (because it is extensively protein bound).
Methimazole* is preferred if treating fetal thyrotoxicosis. |
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Term
| What thionamides are used in a thyroid storm? |
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Definition
| Propylthiouracil* and Methimazole* can both be used in a thyroid storm, however, PTU is preferred since it blocks conversion of T4 to T3 and can control symptoms causes by thyroid excess. |
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Term
| What is Potassium Iodide used for? |
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Definition
Treatment of thyroid storm
Preparation of hyperthyroid patients for surgical resection of the thyroid (pre-operatively) (decreases the vascularity and size of the thyroid gland)
Protect the thyroid gland against radioactive iodine uptake |
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Term
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Definition
Sudden exposure to excess iodide inhibits organification of iodide and further synthesis of thyroid hormone. Excess serum iodide also inhibits release of preformed hormones useful for thyroid storm.
Not for long-term therapy, the results are transient and the throid ceases to respond after a few weeks. |
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Term
| What is Radioiodine (131I) used for? |
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Definition
Because the thyroid gland very avidly takes up iodine, a dose of radioactive iodine can ABLATE thyroid tissue, which results in permanent reduction of thyroid tissue.
Used in DEFINITIVE treatment of Graves' disease, patients with severe cardiac problems, adenomas, and those intolerant to thionamides. |
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Term
| What is used as pretreatment before using Radioiodine (131I)? |
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Definition
| Pretreatment with thionamides is recommended especially in older patients |
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Term
| What does Radioiodine (131I) cure 90% of the time? |
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Definition
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Term
| What are the CIs of Radioiodine (131I)? |
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Definition
| Radioactive iodine should not be used in pregnant women or nursing mothers. |
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Term
| What is thyroid surgery used to treat? |
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Definition
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Term
| How is a thyroid storm managed? |
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Definition
Supportive therapy (fluids, oxygen)
Propranolol (beta blocker to manage hypertension/tachycardia & prevent conversion of T4 to T3)
Propylthiouracil* or Methimazole*
Potassium iodide (to inhibit release of preformed T3 & T4; wait 2-4 hours otherwise the hyperactive gland will take up the iodide to make more T4)
Corticosteroids (Dexamethosone or Hydrocortisone to inhibit peripheral conversion of T4 to T3)
Antibiotics |
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