Background: Hyperkalemia is a common yet dangerous phenomenon in patients with chronic kidney disease (CKD). Patients suffering from CKD are therefore often treated with potassium-binding supplements such as calcium polystyrene sulfonate (CPS). Hypercalcemia is a known side effect of CPS. However, the increase in serum calcium is usually small.
Case description: A 68 year old male patient suffering from CKD was treated with a daily administration of 80mg CPS. He presented with complaints of a dry mouth, thirst and malaise. Blood tests showed an elevated serum calcium of 3,25 mmol/L (2,15- 2,55 mmol/L). Additional diagnostics revealed no abnormalities. The hypercalcemia was attributed to the use of CPS only after the exclusion of a wide differential diagnosis.
Conclusion: Although CPS induced hypercalcemia is usually mild, a more severe course is possible. Knowledge about the composition of medication is paramount to prevent such side effects.