Ingested fluoride has a corrosive effect on the epithelial lining of the gastrointestinal tract, due, in part, to highly corrosive hydrofluoric acid formed in the stomach. Edema, ulceration, and hemorrhage commonly result. Thirst, abdominal pain, vomiting, and diarrhea, with blood in the vomitus and feces usually occur. Absorbed fluoride ion reduces extracellular fluid concentrations of calcium and magnesium. Hypocalcemia sometimes results in tetany.
Hyperkalemia is sometimes a serious threat to the heart.
Cardiac arrhythmias and shock are often prominent features of poisoning. These probably result from combinations of effects of fluid and electrolyte disturbances and direct actions of fluoride on heart and vascular tissues. Hypotension and severe arrhythmias, sometimes progressing to ventricular fibrillation, characterize severe poisonings. Toxic actions on the brain are manifest as headache, muscular weakness, salivation, nystagmus, dilated pupils, lethargy, stupor and coma. Occasionally, convulsions occur.