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18 Cards in this Set
- Front
- Back
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Mechanism of Action of thioamides
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Block the synthesis of thyroid hormones via the iodination of tyrosine residues of thyroglobulin and coupling of MIT and DIT
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Thioamides
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Propylthiouracil and Methimazole
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Onset of action of thioamides
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Slow onset with 3-4 wks for full effect. This is because they do not block the release of preformed hormone
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This antithyroid drug contraindicated in pregnant women due to its crossing the placenta.
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Methimazole
PTU may be used instead, but should still be monitored |
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Severe reactions of Thioamides
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Vasculitis, agranulocytosis, hypothrombinemia, and liver dysfunction
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Action of Iodides
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Inhibit the iodination of tyrosine in the colloid and thyroid hormone release within the follicular cell
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Thyroidal peroxidase
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Converts Iodide ion to iodine
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Onset of action of Iodide salts
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Rapid: 2-7 days. This is due to blocking the synthesis and release of the hormone
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Used in the management of thyroid storm and before surgical resection of the
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Iodide salts
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Adverse rxns of iodide salts
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rash, fever, metallic taste, bleeding disorder
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Who should radioactive iodine not be used in?
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Pregnant and nursing women
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Produces a permanent cure of thyrotoxicosis without surgery
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131-I
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Rapidly supresses the conversion of T4 to T3 in the liver, kidney and other peripheral tissues
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Iodinated radiocontrast media
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Useful in treating pts with thyrotoxicosis induced tachycardia
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Propanolol
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Iodinated radiocontrast media
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Diatrizoate and Iohexol
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Anti-arrhythmic drug that blocks the conversion of T4 to T3
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Amiodarone: Contains Iodine
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How does amiodarone induce hyperthyroidism as well as hypothyroidism?
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Hyperthyroidism may be induced via an iodine-induced mechanism in people with an underlying thyroid disease such as multinodular goiter. This is treated with thioamides.
It may also occur via inflammation of the thyroid that causes it to leak hormones. This is treated with corticosteroids. |
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When initiating T4 therapy for an elderly pt with long standing hypothyroidism, it is important to begin with small doses to avoid?
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Overstimulation of the heart
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