Tapazole - Methimazole

Tapazole methimazole. taprostene [inn] (CG 4203) is a prostaglandin and synthetic analogue of prostacyclin (PGI2). It is a prostanoid RECEPTOR AGONIST that iS a PLATELET AGGREGATION INHIBITOR and claimed to be cardioprotective. 

Figure 1 Basic chemical stmctures of growth promoters and endocrine dlsmptors. (a) 17 P-estradiol, (b) 17 p testosterone, (c) progesterone, (d) cortisol (hydrocortisone), (e) clenbuterol, (1) mabuterol, (g) cimaterol, (h) methylthiouracil, (i) tapazole (methimazole), (j) nonoxynol-9, (k) genistein (isoflavone), and (1) coumestrol (coumestane).

Methimazole (Tapazole) Potassium iodide [Lugol Solution] (SSKI, Thyro-Block)... 

Methimazole (Tapazole) [Antithyroid Agent] Uses Hyperthy-roidism, thyrotoxicosis, pr for thyroid surgery or radiation Action Blocks T3 T4 formation Dose Adults. Initial 15-60 mg/d PO tid Maint 5-15 mg PO daily Peds. Initial 0.4-0.7 mg/kg/24 h PO tid Maint V h- U h of initial dose PO daily w/ food Caution [D, +/-] Contra Breast-feeding Disp Tabs SE GI upset, dizziness, blood dyscrasias Interactions t Effects OF digitalis glycosides, metoprolol, propranolol X effects OF anticoagulants, theophylline X effects W/ amiodarone EMS None OD May cause N/V, HA, abd pain, fever, and pale skin symptomatic and supportive... 

Levothyroxine is taken orally or intravenously and is normally prescribed to treat hypothyroidism or to suppress the release of thyroid hormone so as to manage cancerous thyroid nodules (i.e., thyroid cancer) and growth of goiters. Other less frequently prescribed thyroid and parathyroid drugs include methimazole (Tapazole), various iodides, lithioronine (Triostat), and liotrix (Thyrolar). 

Oral available as capsules and solution Methimazole (generic, Tapazole)... 

The most important and powerful thyreostatic drugs used hitherto are the thiouracil analogues, such as thiouracil, methylthiouracil, propylthiouracil, and phenylthiouracil and die mercaptoimidazole analogues such as tapazole or methimazole. New thyreostatics as mercaptobenzimidazole are said to have been misused recently in some EU countries. 

The antithyroid compounds currently used in the United States are propylthiouracil (6- -propylthiouracil) and methimazole (/-methyl-2-mercaptoimidazole Tapazole). In Great Britain and Europe, carbimazole (Neo-mercazole), a carbethoxy derivative of methimazole, is available, and its antithyroid action is due to its conversion to methimazole after absorption. Measurements of the course of organification of radioactive iodine by the thyroid show that absorption of effective amounts of propylthiouracil follows within 20 to 30 minutes of an oral dose, and that the duration of action of the compounds used clinically is brief. The effect of a dose of 100 mg of propylthiouracil begins to wane in 2 to 3 hours, and even a 500-mg dose is completely inhibitory for only 6 to 8 hours. As little as 0.5 mg of methimazole similarly decreases the organification of radioactive iodine in the thyroid gland, but a single dose of 10 to 25 mg is needed to extend the inhibition to 24 hours. 

Thionamides are the most important class of antithyroid compounds in clinical practice used in nondestructive therapy of hyperthyroidism. These agents are potent inhibitors of TPO, which is responsible for the iodination of tyrosine residues of thyroglobulin and the coupling of iodotyrosine residues to form iodothyronines. These drugs have no effect on the iodide pump or on thyroid hormone release. The most clinically useful thionamides are thioureylenes, which are five- or six-membered heterocyclic derivatives of thiourea and include the thiouracil 6-n-propyl-2-thiouracil (PTU) and the thioimidazole 1-methyl-2-mercaptoimidazole (methimazole, Tapazole, MMI). The uptake of these drugs into the thyroid gland is stimulated by TSH and inhibited by iodide. 

Propylthiouracid (PTU) and methylthiouracil (Tapazole) are effective thioamide antithyroid dmgs used for treating thyrotoxic crisis and in preparation for subtotal thyroidectomy. Methimazole does not inhibit peripheral conversion of T4 to T3 as does PTU, but it is 10 times more potent and has a longer half-life than PTU. Prolonged use of thioamides may cause a goiter because of the... 

Our motivation for investigating thioamide derivatives, which potentially can form N-H... S interactions, arises from the presence of the -N(H)-C(=S)- residue, and derivatives thereof, in several dmgs [20], see Scheme 6.2 for chemical structures of these species. Thus, the antithyroid drugs 6-n-propyl-thiouracil (I) and l-methyl-3//-imidazole-2-thione (II, Methimazole , also marketed as Tapazole ) feature the -N(H)-C(=S)- functional group [21]. Hyperthyroidism may be treated with 3-methyl-2-thioxo-4-imidazoline-l-carboxylate (III, Carbimazole ) which is metabolised in vivo to the active form, known as Methimazole [22]. Anti-tubercular agents containing the thioamide residue and which inhibit mycolic acid synthesis include 2-ethyl-thioisonicotinamide (IV, Ethionamide ) and its -propyl derivative (Prothionamide ) [23-25]. 

Scheme 6.2 Chemical structures of drugs containing the -N(H)-C(=S>- residue and derivatives thereof ( ) 6-n-propyl-thiouracil, (11) 1-methyl-3H-imidazole-2-thione (Methimazole or Tapazole ), (Ilf) ethyl 3-methyl-2-sulfanylidene-imidazole-1 -carboxylate (Carbimazole ) and (IV) 2-ethylpyridine-4-carbothioamide (Ethionamidd )...

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