Metronidazole (1-β-hydroxyethyl-2-methyl-5-nitroimidazole; Flagyl, May & Baker Ltd.), an effective trichomonicidal agent, has recently been credited with widespread metabolic and endocrine effects including biochemical and clinical improvement of thyrotoxicosis (Taylor, 1962, 1965). Harden, Chisholm & Cant (1967), however, found no antithyroid action in either healthy volunteers or thyrotoxic patients but noted improvement of exophthalmos in 9 of 13 patients. The present trial was undertaken to establish the effect of metronidazole on exophthalmos.
Twenty thyrotoxic patients were selected; all had established exophthalmos with a minimum exophthalmometer reading of 20 mm. The patients had all been treated for thyrotoxicosis between 1·5 and 17 yr. previously (mean 5·9 yr.), either with radioactive iodine (14), surgically (3) or with antithyroid drugs (3). At the time of inclusion in the trial 6 patients were euthyroid and 11 were hyperthyroid and receiving antithyroid drugs; three had become hypothyroid after radioactive iodine therapy and were receiving thyroxine.