Methimazole

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

MMI and PTU can lead to methimazole embryopathy with choanal or esophageal atresia. In pregnant women the antithyroid diug dose should be minimized to prevent fetal hypothyroidism by maintaining the maternal free thyroxine serum level slightly above the upper limit of normal. 

Antithyroid drags have several side effects. The most frequent side effects are maculopapular rashes, pruritus, urticaria, fever, arthralgia and swelling of the joints. They occur in 1-5% of patients [1, 2]. Loss of scalp hair, gastrointestinal problems, elevations of bone isoenzyme of alkaline phosphatase and abnormalities of taste and smell are less common. The incidence of all these untoward reactions is similar with MMI and PTU. Side effects of MMI are dose-related, whereas those of PTU are less clearly related to dose [1]. PTU may cause slight transient increases of serum aminotransferase and y-glutamyl transpeptidase concentrations but also severe hq atotoxicity whereas methimazole or carbimazole can be associated with cholestasis. The side... 

Hyperthyroidism (thyrotoxicosis), defined as excessive thyroid activity, causes a state of thyroid hormone excess (thyrotoxicosis) characterized by an increased metabolic rate, increase in body temperature, sweating, tachycardia, tremor, nervousness, increased appetite and loss of weight. Common causes of hyperthyroidism are toxic multinodular goiter, toxic adenoma or diffuse toxic goitre ( Graves disease). Antithyroid diugs (methimazol, carbimazole, propylthiouracil) block thyroid hormone production and are hence suitable for the treatment of hyperthyroidism. 

There is an additive bone marrow depression when methimazole or propylthiouracil is administered with otiier bone marrow depressants, such as the antineo-plastic drugs, or witii radiation therapy. When methimazole is administered with digitalis, there is an increased effectiveness of the digitalis and increased risk of toxicity. There is an additive effect of propylthiouracil when the drug is administered with lithium, potassium iodide, or sodium iodide When iodine products are administered with litiiium products, synergistic hypotiiyroid activity is likely to occur. 

Agranulocytosis is potentially the most serious adverse reaction to methimazole and propylthiouracil. The nurse notifies the primary health care provider if fever, sore throat, rash, headache, hay fever, yellow discoloration of the skin, or vomiting occurs. 

If Hie patient experiences a rash while taking methimazole or propylthiouracil, tlie nurse carefully documents Hie affected areas, noting size, texture, and extent of tlie rash, and reports tlie occurrence of Hie rash to tlie primary health care provider. Soothing creams or lubricants may be applied, and soap is used sparingly, if at all, until Hie rash subsides. 

Ms. Coker, age 38 years, is prescribed methimazole for hyperthyroidism. Discuss important preadministra-tion assessments for Ms. Coker. 

Allergy mediated by selective IgE to certain types of NSAIDs by which symptoms are caused exclusively by a specific group of NSAIDs and no cross-reactivity exists with the other groups of anti-inflammatories. In a study carried out with 26 methimazole-allergic patients with IgE-mediated reactions [33], 14 of which developed anaphylaxis, BAT showed a sensitivity of 42% with an optimum specificity of 100%. No other validated in vitro test exists to date for the diagnosis of this disorder and so it represents an essential aid to diagnosis. 

Tomasi I, I Artaud, Y Bertheau, D Mansuy (1995) Metabolism of polychlorinated phenols by Pseudomonas cepacia ACllOO determination of the first two steps and specific inhibitory effect of methimazole. J Bacterial 111 307-311. 

Alternative—methimazole 30 mg enterally every 6-8 h. Reduce dose once signs/symptoms are controlled. Usual maintenance dose is 15-60 mg daily in three equally divided doses... 

Amiodarone, ampicillin, amoxicillin, captopril, chlorpro-mazine, ceftriaxone, erythromycin estolate, estrogen products, methimazole, nafcillin, rifampin, sulfonamide antimicrobials, and sulfonylureas... 

Acetazolamide, allopurinol, aspirin, captopril, carbamazepine, chloramphenicol, chlorpromazine, dapsone, felbamate, gold salts, metronidazole, methimazole, penicillamine, pentoxifylline, phenothiazines, phenytoin, propylthiouracil, quinidine, sulfonamide antimicrobials, sulfonylureas, and ticlopidine... 

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. 

Application of free halogens such as Br2, IC1, IBr, I2 is also useful for synthesis of these dications.152 Interaction of the drug methimazole 152 with I2 gives dication disulfide 153 and monocation 154 depending on acidity of reaction media (Scheme 57).153... 

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... 

The answer is c. (Hardman, p MOL) Propylthiouracil is more strongly protein bound and crosses the placenta to a lesser degree than methimazole and is, therefore, the safest antithyroid drug in pregnancy... 

If thyroidectomy is planned, propylthiouracil (PTU) or methimazole (MMI) is usually given until the patient is biochemically euthyroid (usually 6 to 8 weeks), followed by the addition of iodides (500 mg/day) for 10 to 14 days before surgery to decrease the vascularity of the gland. Levothy-roxine may be added to maintain the euthyroid state while the thiona-mides are continued. 

Propylthiouracil Methimazole Sodium iodide Lugol s solution... 

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