Hyperthyroidism drugs used

Factors that may enhance theophylline clearance and result in the need for higher doses include tobacco and marijuana smoking, hyperthyroidism, and use of drugs such as phenytoin, phenobarbital, and rifampin. 

Drugs used for hyperthyroidism can be classified as drugs that suppress thyroid hormone synthesis in the anterior lobe of the hypophysis, and they consist of diiodotyrosine and iodine, as well as drugs that suppress thyroid hormone synthesis in thyroid glands (propylthiouracil, methylthiouracil, methimazole, and carbimazole). 

The clinical manifestations of hyperthyroidism and hypothyroidism are listed in Table 31-2. From a pharmacotherapeutic standpoint, hyperthyroidism is treated with drugs that attenuate the synthesis and effects of thyroid hormones. Hypothyroidism is usually treated by thyroid hormone administration (replacement therapy). The general aspects and more common forms of hyperthyroidism and hypothyroidism are discussed here, along with the drugs used to resolve these primary forms of thyroid dysfunction. 

Q8 Comment on the drugs used to treat hyperthyroidism. Your answer should include examples and their mechanisms of action. 

Iodine deficiency causes an increase in the ratio of MIT to DIT in thyroglobufin and leads to a relative increase in the production of T3. Because T3 is more potent than T4, the increase in T3 production in iodine-depleted areas may be beneficial. The thionamide drugs used to treat hyperthyroidism inhibit thyroid peroxidase and thus block thyroid hormone synthesis. 

List the principal drugs used in the treatment of hyperthyroidism and compare the onset and duration of their action. 

The thyroid secretes two types of hormones iodine-containing amino acids (thyroxine and triiodothyronine) and a peptide (calcitonin). Thyroxine and triiodothyronine have very general effects on growth, development, and metabolism. Calcitonin is important in calcium metabolism and is discussed in Chapter 41. This chapter describes the drugs used in the treatment of hypothyroidism and hyperthyroidism (Figure 38-1). 

Differences in physiology, especially in enzyme activity, account for a significant amount of this variability. For example, the chemical 6-propylthiopurine, a drug used to treat hyperthyroidism, is metabolized through a specific pathway in the mouse to a potent carcinogen. However, humans metabolize the chemical differently, and the metabolic products (known as metabolites) do not cause cancer. In this case, using the mouse data to set safe levels in humans would greatly overestimate the toxicity of the chemical to humans. 

Beta-adrenoceptor blockers represent a very important group of drugs used in the treatment of several cardiovascular diseases and hyperthyroidism. Sometimes their use is limited by the occurrence of side effects, such as fatigue in the lower extremities, general tiredness the pathogenesis of these symptoms is unclear. 

Hyperthyroidism may be treated in several ways. One of these is interference with the synthesis of the thyroid hormones, possibly by removal of iodine. Thiourea and cyclic thioureas have this effect and of such cyclic compounds, thiouracil (1030 R = H), its 6-alkyl derivatives (1030 R = Me or Pr) and thiobarbital (1031) are effective thyroid drugs. Today only propylthiouracil (1030 R = Pr) is widely used, probably because it has fewer side effects than the others (71MI21302). The thiouracils are made by the Principal Synthesis from a /3-oxo ester (1032 R = H, Me, Pr, etc.) and thiourea (45JA2197) their fine structures are experimentally based (64AF1004). 

The drug is contraindicated in die presence of an allergy to die drug, pregnancy (Category C), lactation, and phenylketonuria (oral form only). Linezolid is used cautiously in patients with bone marrow depression, hepatic dysfunction, renal impairment, hypertension, and hyperthyroidism. 

These drugp are contraindicated in patients with known hypersensitivity to die drugs, asthma, peptic ulcer disease, coronary artery disease, and hyperthyroidism. Bethanecol is contraindicated in those with mechanical obstruction of die gastrointestinal or genitourinary tracts. Fhtients with secondary glaucoma, iritis, corneal abrasion, or any acute inflammatory disease of the eye should not use die ophtiialmic cholinergic preparations. 

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). 

Stimulants should be initiated at recommended starting doses and titrated up with a consistent dosing schedule to the appropriate response while minimizing side effects (Table 39-2). Generally, stimulants should not be used in patients who have glaucoma, severe hypertension or cardiovascular disease, hyperthyroidism, severe anxiety, or previous illicit or stimulant drug abuse. Further, stimulants can be used, albeit cautiously, in patients with seizure disorders, Tourette s syndrome, and motor tics.14... 

Some neonates born to mothers with Graves disease will be hyperthyroid at delivery. Antithyroid drug therapy (propylthiouracil 5-10 mg/kg per day or methimazole 0.5-1 mg/kg per day) may be required for up to 12 weeks. One drop per day of SSKI may be used in the first few days to rapidly reduce thyroid hormone synthesis and release. 

In the hyperthyroid patient, relieving signs and symptoms and achieving a euthyroid state are the desired outcomes. The method of achieving these outcomes may change over time with the use of antithyroid drugs versus radioactive iodine. 

The answer is d. (Hardman, pp 1398-MOO.) Methimazole is classified as a thioamide and is used in the treatment of hyperthyroidism It prevents the organification of F by blocking the oxidation of F to active I and also inhibits coupling of iodotyrosines. Excessive treatment with this drug may induce hypothyroidism. Some other adverse reactions reported for... 

Blockers are usually used as adjunctive therapy with antithyroid drugs, RAI, or iodides when treating Graves disease or toxic nodules in preparation for surgery or in thyroid storm. /3-Blockers are primary therapy only for thyroiditis and iodine-induced hyperthyroidism. 

Antithyroid drugs are not routinely used after RAI because their use is associated with a higher incidence of posttreatment recurrence or persistent hyperthyroidism. 

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