Isolated hyperphosphatemia potentially associated with long-term use of amlodipine-containing medication: A case report

Calcium channel blockers are commonly used to treat hypertension, a leading cause of illness and death worldwide. Amlodipine is among the most frequently prescribed drugs in this category. We report a case of isolated hyperphosphatemia that occurred in temporal relation to long-term use of a medication containing amlodipine as the active ingredient. A 43-year-old woman was found to have markedly elevated serum phosphate levels during routine laboratory testing, whereas her renal function, calcium, parathyroid hormone, and vitamin D levels were within normal ranges. Secondary causes of hyperphosphatemia were ruled out. The patient was asymptomatic. After discontinuing the amlodipine-containing medication and initiating a dihydropyridine calcium channel blocker (nifedipine), serum phosphate levels returned to normal and remained stable during follow-up. This observation suggests a possible link between long-term amlodipine use and isolated hyperphosphatemia. The finding should be viewed as hypothesis-generating, and additional studies are necessary to clarify the underlying mechanisms.