D2.1 State and explain how excess acidity in the stomach can be reduced by the use of different bases.

Definition: What are Antacids?

  • Antacids are basic medications which do not require a doctor's prescription for usage
  • Usually administered orally
  • Restores the pH balance in your stomach by neutralizing the Hydrochloric acid (HCl) of pH 1-2 in the stomach
  • Relieves symptoms of heartburn, indigestion and other stomach issues (e.g. sour and upset stomachs) when the pH level in your stomach is overly low (acidic)
  • They merely need to employ the use of weak bases
  • Must be taken occasionally, under proper circumstances, or may cause permanent damage to the heart, kidney or bones
  • Minor side effects include headaches and nausea. Side effects occur very rarely if the antacid is used moderately

How Do They Work?
Our stomach usually has a pH of around 2~3 because of the acidic environment. When the pH drops below that, we experience discomfort. An antacid is a base that will neutralize the excess acid to bring the pH level back to around 3~4.
Bromo Seltzer is an example of an antacid that uses sodium compounds.
Bromo Seltzer is an example of an antacid that uses sodium compounds.

Examples are provided below.

  • Aluminum compounds usually include carbonate, hydroxide, or phosphate. (Could cause constipation)
  • Equation: Al(OH)3 + 3HCl → AlCl3 + 3H2O

  • Magnesium compounds can come in many forms, such as carbonate, hydroxide, oxide, trisilicate and aluminosilicate. (Has laxative(excrement-inducive) properties)
  • Equation: MgCO3 + 2HCl → MgCl2 + 2H2O
  • Equation: Mg(OH)2(s) + 2 HCl(aq) -----> MgCl2(aq) + 2 H2O(l)

  • Two of the most commonly known calcium antacids are calcium carbonate and calcium phosphate.
  • Equation: CaCO3 + 2HCl → CaCl2 + H2O + CO2

Differences in Antacids:
Antacids containing magnesium hydroxide and sodium bicarbonate dissolve rapidly in the stomach and will therefore bring the fastest relief.

Antacids containing calcium carbonate or aluminum hydroxide take longer to dissolve, however the antacid functions for a longer period of time.

When an antacid stays in the stomach for a long time or if it is taken after a meal, it will function for a longer period of time.

Alginates & Anti-Foaming Agents!
In addition, the uses of alginates and anti-foaming agents are to prevent damage of the stomach and esophageal linings.
By using alginates, which float on the acid layer, the stomach and parts of the esophagus are coated even in the event of acid reflux, creating another layer of protection.
Anti-foaming agents work to prevent foam that would rise easier, and carry the stomach acid with it. An additive which reduces the surface tension of a solution or emulsion, thus inhibiting or modifying the formation of a foam. Commonly used agents are insoluble oils, dimethyl polysiloxanes and other silicones, certain alcohols, stearates and glycols. The additive is used to prevent formation of foam or is added to break a foam already formed. As many reactions between antacids and hydrochloric acid result in the production of CO2, the anti-foaming agent is necessary to prevent vomiting which may be caused by the formation of a foam layer of gas in the stomach. Instead, the bubbles are broken and the gas rises as foam, which is what causes burping after taking particular types of antacids.

NOTE: The altered pH due to antacids may affect the effects of other drugs that are taken oraly