View source for Methimazole

{{MedTemplate
| generic           = Methimazole (thiamazole)
| brand             = Tapazole; outside US Mercazole
| structure         =
| classes           = [[:Category:Antithyroid_agents|Antithyroid agent]], [[:Category:Thionamides|Thionamide]]
| uses              = <vote slug="hyperthyroidism-use">Hyperthyroidism (Graves disease, toxic nodular goiter)</vote>, <vote slug="thyroid-storm-use">Thyroid storm (with PTU often preferred acutely)</vote>, <vote slug="preoperative-thyroidectomy-use">Preoperative thyroid preparation</vote>, <vote slug="preradioiodine-treatment-use">Pre-radioiodine treatment</vote>
| starting_dose     = 10-40 mg PO daily depending on hyperthyroidism severity; titrate by clinical and biochemical response (target TSH/free T4)
| preparations      = 5, 10 mg tablets
| fda_max           = 60 mg/d typical
| pill_id           =
| routes            = Oral
| onset             = Biochemical improvement within 2-4 weeks; full euthyroid state 6-12 weeks
| duration          = 24 hours
| halflife          = ~4-6 hours (plasma); intrathyroidal accumulation gives a much longer functional duration<ref name="tapazole-label">FDA Prescribing Information, Tapazole (methimazole), Pfizer/King, current revision. https://www.accessdata.fda.gov/drugsatfda_docs/label/2016/007599s029lbl.pdf</ref>
| bioavailability   = ~93% (oral)<ref name="tapazole-label" />
| pregnancy         = '''Avoid in first trimester''' (aplasia cutis, choanal/esophageal atresia association); switch to PTU in first trimester, then back to methimazole in second/third for lower PTU hepatotoxicity risk.{{citation needed}}
| legal             = [[USLegal:Prescription only|Rx-only]] in US
| mechanism         = <vote slug="methimazole-mech-claim">Methimazole inhibits thyroid peroxidase (TPO), blocking iodination of thyroglobulin tyrosine residues and the coupling of mono- and diiodotyrosine to form T3 and T4; the result is reduced new hormone synthesis. Unlike propylthiouracil, methimazole does not inhibit peripheral T4-to-T3 conversion.</vote> Agranulocytosis is the most-feared adverse effect (~0.3%, usually first 90 days of treatment; warn patients to seek urgent CBC for fever or severe sore throat). Hepatotoxicity is class-recognized but more often associated with PTU<ref name="tapazole-label" />.
}}

== References ==
<references />
[[Category:Antithyroid agents]]
[[Category:Thionamides]]