Antithyroid drug

Hyperthyroidism (excessive production of thyroid hormones) asually requires surgery, but before. surgery the patient mu.st be prepared by preliminary abolition of the hyper-thyroidi.sm through the use of antithyroid drugs. Thiourea and related eompounds. show an antithyroid activity, but they arc too toxic for clinical use. The more useful drugs are 2-thiouracil derivatives and a closely related 2-thioimidazolc derivative. All of these appear to have a similar mechanism of action (i.c.. prevention of the iodination of the precursors of thyroxine and triiodothyronine). The main difference in the compounds lies in their relative toxieities. 

These compounds are absorbed well after oral administration and excreted in the urine. 

The 2-thiourdcil.s, 4-keto-2-thiopyrimidines. are undoubtedly tautomeric compounds and can be represented as fol-low.s  

Some 300 related structures have been evaluated for antithyroid activity, but of these, only the 6-alkyl-2-thiouracil and closely related structures possess useful clinical activity. The most serious adverse effect of thiouracil therapy is agranulocytosi.s. 

PropyfthiouradI, USP. Propylthiouracil. 6-propyl-2-thiouracil (Propacil), is a. stable, white, crystalline powder with a biner taste. It is slightly soluble in water but readily soluble in alkaline solutions (salt formation). 

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Imidazole, 1 -hydroxy-2,4,5-triphenyl-3-oxides reactions, S, 455 Imidazole, iodo-nitrodehalogenation, 5, 396-397 Imidazole, 1-iodo-reactions, S, 454 stability, S, 110 Imidazole, 2-iodo-synthesis, S, 401 Imidazole, N-iodo-, S, 393 reactions, 5, 454 Imidazole, 4-iodo-5-methyl-iodination, 5, 400 Imidazole, 2-isopropyl-4-nitro-N-nitration, 5, 351 Imidazole, 2-lithio-reactions, S, 106, 448 Imidazole, 2-mercapto-l-methyl-as antithyroid drug, 1, 171 mass spectra, 5, 358 Imidazole, 1-methoxymethyl-acylation, S, 402 Imidazole, 5-methoxy-l-methyl-reactions... 

Phenytoin, trimethadione, valproic acid Antithyroid drugs Methimazole Chelators... 

Remission after antithyroid drug treatment In 40-50% of patients 1 year after treatment withdrawal No remission... 

Antithyroid drug treatment 1 year Until euthyroid... 

Treatment with radioiodine or surgery If relapse after 1 year of antithyroid drug treatment After euthyroid ism is achieved... 

No significant interactions have been reported when tiie expectorants are used as directed. The exception is iodine products. Lithium and other antithyroid drug may potentiate the hypotliyroid effects of these drug if used concurrently with iodine products. When potassium-containing medications and potassium-sparing diuretics are administered with iodine products, the patient may experience hypokalemia, cardiac arrhythmias, or cardiac arrest. Thyroid function tests may also be altered by iodine... 

Discuss the uses, general drug actions, adverse reactions, contraindications, precautions, and interactions of thyroid and antithyroid drugs. 

Discuss important preadministration and ongoing assessment activities the nurse should perform on the patient taking thyroid and antithyroid drugs. 

Discuss ways to promote an optimal response to therapy, how to manage adverse reactions, and important points to keep in mind when educating patients about the use of thyroid and antithyroid drugs. 

SUMMARY DRUG TABLE THYROID AND ANTITHYROID DRUGS... 

Antithyroid drugp or thyroid antagonists are used to treat hyperthyroidism. In addition to the antithyroid drugs, hyperthyroidism may be treated by the administration of strong iodine solutions, use of radioactive iodine (131I), or by surgical removal of some or almost all of the tiiyroid gland (subtotal thyroidectomy). 

Antithyroid dru inhibit the manufacture of thyroid hormones. They do not affect existing tiiyroid hormones tiiat are circulating in die blood or stored in die thyroid gland. For tiiis reason, therapeutic effects of the antithyroid drugs may not be observed for 3 to 4 weeks. Antithyroid drugs are listed in the Summary Drug Table Thyroid and Antithyroid Drugs. 

Before a patient starts therapy with an antithyroid drug, die nurse obtains a history of the symptoms of hyperthyroidism. It is important to include vital signs, weight, and a notation regarding the outward symptoms of die hyperthyroidism (see Table 51-1) in the physical assessment. If die patient is prescribed an iodine solution, it is essential that die nurse take a careful allergy history, particularly to iodine or seafood (which contains iodine). 

Once a euthyroid state is achieved, tlie primary health care provider may add a thyroid hormone to tlie therapeutic regimen to prevent or treat hypothyroidism, which may develop slowly during long-term antithyroid drug therapy or after administration of 131I. 

The patient with hyperthyroidism is likely to have cardiac symptoms such as tachycardia or palpitations. Propranolol, a adrenergic blocking drug (see Chap. 21), may be prescribed by tlie primary health care provider as adjunctive treatment for several weeks until tlie therapeutic effects of tlie antithyroid drug are obtained. 

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