Methimazole pharmacology in man: Studies using a newly developed radioimmunoassay for methimazole

David S Cooper, H. H. Bode, B. Nath, V. Saxe, F. Maloof, E. C. Ridgway

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A RIA for the antithyroid drug methimazole [1-methyl-2-mercaptoimidazole (MMI)] has been developed. A MMI derivative, 5-COOH-MMI, was conjugated to porcine thyroglobulin, and antibodies to the conjugate were raised in rabbits. [35S]MMI was used as the tracer. At a final antibody dilution of 1:100, the assay could detect MMI in amounts as low as 2.5 ng. The putative MMI metabolites 3-methyl-2-thiohydantoin and 1-methylimidazole had minor cross-reactivities of 2.1% and 0.5%, respectively. There was no effect of serum proteins on MMI immunoactivity. MMI was given orally to normal subjects (n = 6), hyperthyroid patients (n = 5), patients with hepatic cirrhosis (n = 4), and normal lactating women (n = 4). After a single dose of 60 mg, peak MMI levels were similar in the normal subjects and the hyperthyroid patients (~ 1.5 μg/ml). Patients with hepatic cirrhosis had similar peak MMI serum levels [1.31 ± 0.3 (± SEM) μg/ml], but the half-time of MMI disappearance from serum was significantly prolonged compared with the normal value (21.2 vs. 6.0 h; P <0.001). The lactating women received 40 mg MMI as a single dose. Over the next 8 h, mean MMI levels in serum and milk were nearly identical, with a mean serum to milk ratio of 1.03 ± 0.16. A total of 70.0 ± 6.0 μg MMI was excreted in the milk over the 8-h time period. This amount of MMI could affect neonatal thyroid function.

Original languageEnglish (US)
Pages (from-to)473-479
Number of pages7
JournalJournal of Clinical Endocrinology and Metabolism
Issue number3
StatePublished - 1984
Externally publishedYes


ASJC Scopus subject areas

  • Biochemistry
  • Endocrinology, Diabetes and Metabolism

Cite this

Methimazole pharmacology in man : Studies using a newly developed radioimmunoassay for methimazole. / Cooper, David S; Bode, H. H.; Nath, B.; Saxe, V.; Maloof, F.; Ridgway, E. C.

In: Journal of Clinical Endocrinology and Metabolism, Vol. 58, No. 3, 1984, p. 473-479.

Research output: Contribution to journalArticle