Bicarbonate renal absorption

A variety of adverse effects have been reported following the use of antacids. If sodium bicarbonate is absorbed, it can cause systemic alkalization and sodium overload. Calcium carbonate may induce hypercalcemia and a rebound increase in gastric secretion secondary to the elevation in circulating calcium levels. Magnesium hydroxide may produce osmotic diarrhea, and the excessive absorption of Mg++ in patients with renal failure may result in central nervous system toxicity. Aluminum hydroxide is associated with constipation serum phosphate levels also may become depressed because of phosphate binding within the gut. The use of antacids in general may interfere with the absorption of a number of antibiotics and other medications. 

Because acid-pepsin disease rarely occurs in the absence of gastric acid and pepsin, antacids are highly effective in its overall management. Antacids consist of a mixture of magnesium, aluminum, and calcium compounds. Their efficacy is based on their inherent ability to react with and neutralize gastric acid. Sodium bicarbonate, which may leave the stomach rapidly, can cause alkalosis and sodium retention. Calcium salts may produce hypercalcemia, which can be detrimental in patients with impaired renal function. Aluminum salts may decrease the absorption of tetracyclines and anticholinergic drugs. 

Sodium bicarbonate (eg, baking soda, Alka Seltzer) reacts rapidly with HC1 to produce carbon dioxide and NaCl. Formation of carbon dioxide results in gastric distention and belching. Unreacted alkali is readily absorbed, potentially causing metabolic alkalosis when given in high doses or to patients with renal insufficiency. Sodium chloride absorption may exacerbate fluid retention in patients with heart failure, hypertension, and renal insufficiency. 

Treatment for salicylate intoxication is directed toward (1) decreasing further absorption, (2) increasing elimination, and (3) correcting add-base and electrolyte disturbances. Activated charcoal binds aspirin and prevents its absorption. Elimination of salicylate may be enhanced by alkaline diuresis and in severe cases by hemodialysis." Sodium bicarbonate may be given to alleviate metabolic acidosis. Indications for hemodialysis include serum salicylate >1000 mg/L, severe CNS depression, intractable metabolic acidosis, hepatic failure with coagulopathy, and renal failure. ... 

Naproxen is absorbed fully when administered orally. Food delays the rate but not the extent of absorption. Peak concentrations in plasma occur within 2 to 4 hours and are somewhat more rapid after the administration of naproxen sodium. Absorption is accelerated by the concurrent administration of sodium bicarbonate but delayed by magnesium oxide or aluminum hydroxide. Naproxen also is absorbed rectally, but more slowly than after oral administration. The half-life of naproxen in plasma is variable. It is about 14 hours in the young, but it may increase about twofold in the elderly because of age-related decline in renal function. 

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