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13 Cards in this Set
- Front
- Back
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Levothyroxine (T4)
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-hormone of choice
-consistent potency/long DOA (6-7 days) -po (gi absorption variable), parenteral -iron, calcium, aluminum interfere with absorption -intestinal flora alterations -drugs that induce hepatic P450 enzymes enhance excretion -used for suppressive therapy |
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Liothyronine (T3)
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-po (absorption: >95%), parenteral
-used when quicker onset is desired -requires more frequent dosing (1/2 life: 1 day) -more $$$ |
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Liotrix (4:1 ratio of T4 to T3)
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po only
more natural |
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Natural thyroid drugs (armour thyroid)
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-made from dessicated pig thyroid glands
-increasingly popular; patients feel better |
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Major therapeutic uses for hypothyroidism
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-Hashimoto's (autoimmune destruction)
-Myxedema (LT hypothyroidism) Subtotal thyroidectomy -Radioiodine ablation of thyroid -Hypothyroid-related hypercholesterolemia (a classic feature of hypothyroid states) |
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MOA of Thyroid hormone
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1. Free TH enters cell
2. T4 converted to T3 3. T3 enters nucleus 4. Binds to a specific T3 receptor that exists as alpha, beta 5. Effects mediated by activation of nuclear receptors: turn on formation of RNA; leads to subsequent protein synthesis |
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Antithyroid drugs
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-Thioureylenes (thioamide family)
-Individual agents: -PTU: prototype; half life 75 minutes -Methimazole: half life: 4-6 hrs; decreased metabolism with liver disease -complications: agranulocytosis (1/500): granulocytopenia (decreased lymphocytes/monocytes) |
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MOA of antithyroid drugs
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-interfere with oxidation of iodide ion by inhibition of the peroxidase enzyme
-interferes with organification of iodine -requires deletion of iodinated thyroglobulin stores in colloid before clinical effects become evident |
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Major uses of Antithyroid drugs
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-Graves disease (diffuse toxic goiter), an autoimmune disorder; production of TSH-receptor stimulating antibodies (TSI)
-Multinodular goiter |
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Diffuse nontoxic goiter
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-Pathogenesis: outside US
-Iodide deficiency -Treatment: iodide (~50 mg per year) |
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Radioactive iodine (for hyperthyroidism)
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-131I used for radioiodine ablation (1/2 life of 8 days)
-emits gamma rays/beta particles -123I used for thyroid scans (1/2 life of 13 hours)(gamma rays) -oral (solution/capsules) -Concern about potential effects on germ cells may discourage use in young patients under 21 yoa -High incidence of delayed hypothyroidism (80%) MOA: deposited in colloid; emission kills follicular cells |
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Iodides
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-saturated solution of potassium iodide and Lugol's
-used to treat hyperthyroidism -rarely used alone -usually initiated after onset of thiamide therapy -rapid improvements in thyrotoxic symptoms in 2-7 days -used to decrease vascularity and size of hyperplastic gland prior to surgery -Complications: iodism (rash, swollen salivary glands, fever, mucous membranes ulcerations) -used prophylactically when at risk of radiation exposure -can paint back with betadine for 5 days |
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Ipodate/iopanoic acid
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-ER tx of thyroid storm (not approved by FDA for this)
-rapidly inhibit the conversion of T4 to T3 -relatively nontoxic -provide adjunctive tx for thyroid storm (elevated temp, cardiac overload) |
