Severe Hyperphosphatemia Induced by a Phosphate-Containing Oral Laxative

OBJECTIVE: To describe a case of severe hyperphosphatemia following unintentional overdosage with an oral phosphate laxative, and raise attention to the risk of using such medications in the elderly. CASE SUMMARY: An 84-year-old white woman was admitted with confusion 8 hours after inadvertently ingesting 12 fluid ounces of Fleet Phospho-Soda (instead of the prescribed 1 1/2 fluid ounces) prior to a colonoscopy. Her serum phosphate and ionized calcium concentrations were 10.3 mmol/L and 0.56 mmol/L, respectively. She was treated conservatively with oral phosphate binders and made an uneventful recovery. DISCUSSION: Several previous reports have described hyperphosphatemia in association with phosphate laxatives, especially in patients with renal or colonic disease. Our case again presents two important issues in the use of phosphate laxatives by the elderly: (1) the frequently overlooked underlying renal insufficiency in which, despite "normal" serum creatinine values, renal phosphate handling may be impaired; and (2) the potential for drug misuse and poor compliance in the elderly. CONCLUSIONS: Caution should be taken with the use of phosphate laxatives in the elderly in the face of potentially serious metabolic abnormalities that may be generated.