Acidifying drugs are used to correct metabolic alkalosis. Theseinclude:
· acetazolamide (used in treatment of acute mountain sickness)
· ammonium chloride.
Ascorbic acid, along with ammonium chloride, serves as a uri-nary acidifier.
The action of most acidifying drugs is immediate.
Orally administered ammonium chloride is absorbed completely in 3 to 6 hours. It’s metabolized in the liver to form urea, which is excreted by the kidneys.
Acetazolamide inhibits the enzyme carbonic anhydrase, which blocks hydrogen ion secretion in the renal tubule, resulting in in-creased excretion of bicarbonate and a lower pH. Acetazolamide also acidifies urine but may produce metabolic acidosis in normal patients.
Acidifying drugs have several actions:
§ Ammonium chloride lowers the blood pH after being metabo-lized to urea and to hydrochloric acid, which provides hydrogen ions to acidify the blood or urine.
§ Ascorbic acid directly acidifies urine, providing hydrogen ions and lowering urine pH.
§ Acetazolamide increases the excretion of bicarbonate, lowering blood pH.
A patient with metabolic alkalosis requires therapy with an acidi-fying drug that provides hydrogen ions; such a patient may need chloride ion therapy as well.
Most patients receive both types of ions in oral or parenteral dos-es of ammonium chloride, a safer drug that’s easy to prepare.
In patients with renal dysfunction, acetazolamide may be ineffec-tive and cause loss of potassium in urine.
Acidifying drugs don’t cause clinically signifi-cant drug interactions. However, concurrent use of ammonium chloride and spironolac-tone may cause increased systemic acidosis. (See Adverse reactions to acidifying drugs.)