Mechanism of action
As an absorbable antacid, sodium bicarbonate directly reacts chemically with hydrochloric acid ($HCl$) in the stomach, rapidly neutralizing it. However, this process is accompanied by vigorous release of carbon dioxide ($CO_2$).
As an agent affecting excretion, intravenous administration of the drug causes urine alkalinization (increase in renal filtrate pH). According to the ion trapping principle, weak acids (e.g., barbiturates, acetylsalicylic acid, sulfonamides) actively ionize in an alkaline environment. The ionized (polar) form cannot cross the lipid membranes of the renal tubules, loses its ability to undergo passive reabsorption, and is actively eliminated from the body.
Pharmacological effects
The drug provides an immediate, but short-term decrease in gastric juice acidity. Upon systemic absorption, sodium bicarbonate shifts the acid-base balance towards alkalinity, causing systemic alkalosis. When excreted via the kidneys, urine alkalinization forces the elimination of weak acids, which is used to accelerate their clearance in overdoses and poisonings.
Indications for use
Sodium bicarbonate is prescribed for:
- Hyperacid conditions and heartburn (as symptomatic therapy to relieve pain during peptic ulcer exacerbation);
- Poisonings and overdoses with medicinal products possessing weak acid properties (for forced elimination via urine alkalinization);
- Metabolic acidosis.
Side effects and contraindications
Adverse effects:
- Gastric distension caused by the released carbon dioxide, which provokes a secondary increase in hydrochloric acid secretion («rebound» syndrome);
- Development of systemic alkalosis with frequent and uncontrolled intake.
Contraindications:
- Alkalosis of various origins.
Prescription details
The drug is available as 0.3 and 0.5 g tablets. The standard oral dosage is 0.5–1.0 g per dose. In forced diuresis practice and acute poisonings, it is administered parenterally (intravenously) to rapidly alter the pH of the renal filtrate.
Briefly: answers to topical questions
What side effects does sodium bicarbonate cause?
- Systemic alkalosis (alkalosis) — occurs with frequent oral intake.
- Edema and arterial hypertension (hypertensio arterialis) — associated with sodium accumulation during therapy.
- Hypervolemia and pulmonary edema — potential complications when administering the solution intravenously.
- Gas formation and gastric distension — discomfort, belching, and secondary secretion increase due to carbon dioxide release.
In what dosage forms is sodium bicarbonate available for parenteral administration?
- Infusion solution 5%, 50-100 ml — dosage form of sodium bicarbonate for intravenous administration.
Soda is gas and alkali: it rapidly neutralizes acid in the stomach, but causes a «rebound» bloating and alkalinization of the entire body.
Class and exam questions
Why is sodium bicarbonate classified as an absorbable antacid?
Because after the chemical neutralization reaction of hydrochloric acid, the resulting compounds are absorbed into the systemic circulation, capable of causing systemic alkalosis and altering urine pH.
What is the principle of ion trapping in the excretion of weak acids?
In an alkaline urine environment, weak acids ionize, become polar, cannot cross the tubular lipid membranes, are not reabsorbed into the blood, and are excreted from the body.
Why might acid secretion increase after sodium bicarbonate intake?
Neutralization of hydrochloric acid is accompanied by vigorous release of carbon dioxide ($CO_2$), which distends the stomach walls, causing a secondary increase in secretion («rebound» syndrome). Carbonic anhydrase inhibitors
What else to study on this topic
- Comparison of absorbable and non-absorbable antacids (magnesium oxide, algeldrate)
- Pathogenesis of the «rebound» syndrome during sodium bicarbonate intake
- The ion trapping principle for weak bases (using ammonium chloride as an example)
- Effect of carbonic anhydrase inhibitors (acetazolamide) on bicarbonate excretion
- Methods of forced diuresis in barbiturate and salicylate poisonings
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