Formic acid poisoning: case report and in vitro study of the hemolytic activity.

A case of fatal oral poisoning with formic acid resulting in shock, metabolic acidosis, and hemolysis is reported. The formic acid concentration on admission was 348 micrograms/mL, which, together with an increase in lactic acid, contributed to the metabolic acidosis. Because it has been suggested in the literature that formic acid might induce hemolysis via a direct cytotoxic action on the RBCs, an in vitro study was performed using human RBCs in saline, phosphate buffered saline, and plasma in order to define the mechanism of the hemolysis. These experiments indicate that the hemolysis is not a cytotoxic effect of formic acid but is related to the degree of acidity in itself.