Sodium ion concentration in extracellular fluid (Na⁺ concentration (ECF))

The sodium ion concentration in extracellular fluid refers to the amount of sodium ions present outside cells, most commonly measured in blood plasma/serum. Sodium is the predominant extracellular cation and is crucial for maintaining fluid balance, osmotic pressure, nerve conduction, muscle contraction, and blood pressure. Normal plasma sodium is typically 135–145 mmol/L. Pathological increases or decreases in this concentration, termed hypernatremia and hyponatremia, underlie important clinical syndromes. Therapeutics can target sodium concentration indirectly by modifying water or salt handling via the kidney, but this parameter itself is not a classical molecule or drug target.

Other names

Extracellular sodium concentrationSodium concentration (ECF)Serum sodiumPlasma sodium

Drugs alter sodium concentration via effects on renal sodium reabsorption/excretion, water balance (antidiuretics/diuretics), or replacement (IV fluids).