What is the most likely cause of dizziness and heart palpitations in a patient taking enalapril and spironolactone with an eGFR of 48 mL/min?

The most likely cause of dizziness and heart palpitations in a patient taking enalapril and spironolactone, particularly with an estimated glomerular filtration rate (eGFR) of 48 mL/min, is hyperkalemia.

Enalapril is an ACE inhibitor that can contribute to increased potassium levels, especially in patients with reduced renal function, as their ability to excrete potassium is diminished. Spironolactone, a potassium-sparing diuretic, further increases serum potassium levels. When renal function is compromised, such as in this case where the eGFR is significantly below normal (the typical normal range is around 90-120 mL/min), the risk of hyperkalemia is heightened.

Symptoms of hyperkalemia can include dizziness and heart palpitations. These symptoms arise because elevated potassium levels can affect cardiac conduction and lead to arrhythmias, contributing to palpitations, while dizziness may be related to various mechanisms including changes in blood flow or blood pressure.

The other conditions listed—hypernatremia, hyponatremia, and hypercalcemia—are less likely to explain the symptoms in this context. Hyponatremia can potentially lead to dizziness,