reported by some patients receiving 0.8 to 1.6 g (20 to 40 mmol)/ day of potassium chloride either as a wax-matrix tablet (5 of the 17 receiving the treatment) or as a microencapsulated tablet (6 of the 17) (Pietro and Davidson, 1990).

Ulceration of gastrointestinal tract mucosa and perforation of the small bowel have been reported in patients using various potassium chloride supplements (Lambert and Newman, 1980; Leijonmarck and Raf, 1985). In a placebo-controlled trial that provided 2.3 g (60 mmol)/day of microencapsulated potassium to 175 prehypertensive subjects for 6 months, high pill compliance but no serious gastrointestinal effect was reported (Whelton et al., 1995). Overall, the specific product/vehicle appears to be a critical determinant of the risk of gastrointestinal side effects from supplemental potassium.

Cardiac arrhythmias from hyperkalemia are the most serious consequence of excessive potassium intake. The typical sequence of findings is hyperkalemia, followed by conduction abnormalities on electrocardiogram (ECG) and then cardiac arrhythmias, which can be life-threatening. Such consequences result from either a high plasma concentration of potassium or from rapid and extreme changes in its concentration (Kallen et al., 1976). At typical dietary intakes of potassium, the normal range of plasma concentration of potassium is 3.5 to 5.0 mmol/L. The actual level at which hyperkalemia increases the risk of serious arrhythmias is uncertain, but is likely at a level greater than 5.5 mmol/L.

Acute toxicity from accidental or intentional consumption of large quantities of potassium chloride or potassium-containing salt substitutes by apparently healthy individuals has been reported (Kallen et al., 1976; Su et al., 2001; Wetli and Davis, 1978). However, such evidence of acute toxicity is of limited value in assessing the potential hazards from chronic ingestion of high levels of potassium. In clinical trials that assessed the effects of potassium supplementation as high as 15.6 g (400 mmol)/day over a period of at least 5 days in apparently healthy individuals, plasma levels of potassium increased but remained within the normal range (see Table 5-12). Importantly, there were no instances of hyperkalemia reported in these studies.

However, in individuals whose urinary potassium excretion is impaired by a medical condition, drug therapy, or both, instances of life-threatening hyperkalemia have been reported. There have been several case reports of hyperkalemia in individuals who reported