[Tolerance of large doses of oral zinc sulfate]

The toxicity of oral zinc was investigated in patients hospitalized for chronic leg ulcers. Untoward effects were monitored by reference to clinical tolerance, hematological, hepatic and renal parameters, and serum concentrations of copper and iron. The investigation was conducted by comparing two groups of patients who initially did not differ significantly with regard to ulcer area, hemoglobin, leukocytes, copper, iron and zinc. Both groups had serum zinc concentrations in the lower normal range. One group was treated with 3 daily doses of 220 mg oral zinc sulfate and the other with placebo, and hence, untoward effects of zinc should have become manifest in the zinc-treated group. This was not the case. Therefore, oral zinc appears to be well tolerated clinically and does not cause hematological, renal or hepatic toxicity. In view of the increasing interest in and range of indications for zinc, particularly in conditions associated with cellular immunological hyporeactivity, this finding is a prerequisite for the institution of clinical zinc therapy.