Sodium bicarbonate is a systemic alkalinizing agent. It most often is administered IV in the treatment of metabolic and respiratory acidosis. Sodium bicarbonate is also used in the acute treatment of hyperkalemia, although it should be kept in mind that this represents palliative treatment for this condition. Sodium bicarbonate is sometimes used for urinary alkalinization. Despite being a highly effective antacid, sodium bicarbonate is rarely used for the chronic treatment of peptic ulcer disease because it can be absorbed and can affect systemic acid-base balance. Sodium bicarbonate was in use prior to 1938 and approved by the FDA at its inception.
Mechanism of Action: After oral administration, sodium bicarbonate neutralizes hydrochloric acid in the stomach, forming sodium chloride, carbon dioxide, and water. Excess bicarbonate ions are absorbed in the small intestine. Thus, all of a dose of exogenous sodium bicarbonate eventually reaches the extracellular fluid, and a mild alkalosis can result. This usually is corrected quickly by the renal system in patients with normal renal function. After IV administration, sodium bicarbonate dissociates to bicarbonate ions, which constitute the conjugate base portion of the body’s extracellular buffer system (bicarbonate/carbonic acid buffer). Administration of sodium bicarbonate will restore acid-base balance in patients with metabolic or respiratory acidosis; however, metabolic alkalosis can result from the use of sodium bicarbonate.
Excess bicarbonate ions that result from the administration of sodium bicarbonate are excreted in the urine, alkalizing the urine. This alkalization decreases renal absorption and increases the clearance of certain drugs, intoxicants, weak acids, and blood pigments.