Alkalinizing and acidifying drugs
Alkalinizing and acidifying drugs
Alkalinizing and acidifying drugs act to correct acid-base imbalances in the blood. These acid-base imbalances include:
- metabolic acidosis, a decreased serum pH caused by excess hydrogen ions in the ECF, which is treated with alkalinizing drugs
- metabolic alkalosis, an increased serum pH caused by excess bicarbonate in the ECF, which is treated with acidifying drugs.
Odd couple
Alkalinizing and acidifying drugs have opposite effects:
- An alkalinizing drug will increase the pH of the blood and decrease the concentration of hydrogen ions.
- An acidifying drug will decrease the pH of the blood and increase the concentration of hydrogen ions.
Rx for o.d.
Some of these drugs also alter urine pH, making them useful in treating some urinary tract infections and drug overdoses.
Alkalinizing drugs
Alkalinizing drugs are used to treat metabolic acidosis and to increase blood pH. These include:
- sodium bicarbonate
- sodium citrate
- sodium lactate
- tromethamine.
Increasing another pH
Sodium bicarbonate is also used to increase urine pH.
Pharmacokinetics
All of the alkalinizing drugs are absorbed well when given orally.
Metabolism and excretion
Sodium citrate and sodium lactate are metabolized to the active ingredient, bicarbonate. Sodium bicarbonate isn’t metabolized. Tromethamine undergoes little or no metabolism and is excreted unchanged in urine.
Pharmacodynamics
Sodium bicarbonate separates in the blood, providing bicarbonate ions that are used in the blood buffer system to decrease the hydrogen ion concentration and raise blood pH. (Buffers prevent extreme changes in pH by taking or giving up hydrogen ions to neutralize acids or bases.) As the bicarbonate ions are excreted in urine, urine pH rises. Sodium citrate and lactate, after conversion to bicarbonate, alkalinize the blood and urine in the same way.
Remember: A low pH means a solution is acidic, and a high pH means it’s alkaline. Therefore, to raise the pH, you use an alkalinizing drug and, likewise, to lower the pH, you use an acidifying drug.
Hitching up with hydrogen
Tromethamine acts by combining with hydrogen ions to alkalinize the blood; the resulting tromethamine’hydrogen ion complex is excreted in urine.
Pharmacotherapeutics
Alkalinizing drugs are commonly used to treat metabolic acidosis. Other uses include raising urine pH to help remove certain substances, such as phenobarbital, after an overdose.
Drug interactions
The alkalinizing drugs sodium bicarbonate, sodium citrate, and sodium lactate can interact with a wide range of drugs to increase or decrease their pharmacologic effects.
- They may increase excretion and reduce the effects of chlorpropamide, ketoconazole, lithium, and salicylates.
- They may reduce the excretion and increase the effects of amphetamines, flecainide, quinidine, and pseudoephedrine.
- The antibacterial effects of methenamine are reduced when taken with alkalinizing drugs.
Adverse reactions to alkalinizing drugs
Adverse reactions to alkalinizing drugs vary.
Sodium bicarbonate
- Bicarbonate overdose
- Cerebral dysfunction, tissue hypoxia, and lactic acidosis (with rapid administration for diabetic ketoacidosis)
- Water retention and edema
Sodium citrate
- Metabolic alkalosis, tetany, or aggravation of existing heart disease (with overdose)
- Laxative effect (with oral administration)
Sodium lactate
- Metabolic alkalosis (with overdose)
- Extravasation
- Water retention or edema (in patient with kidney disease or heart failure)
Tromethamine
- Hypoglycemia
- Respiratory depression
- Extravasation
- Hyperkalemia
- Toxic drug levels (if given for more than 24 hours)
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