Long-term use of potassium perchlorate.

A case of Graves' disease with potassium perchorate for 22 years without ill effect is described. Thyrotoxicosis recurred 4 weeks after the medication was withdrawn, suggesting that euthyroidism had been maintained by chronic use of the drug. As toxicity of perchlorate is probably dose related, it is suggested that long-term use of low dose perchlorate may be no more hazardous than alternative antithyroid therapy.