Role of antacids
1. Gastrointestinal hyperacidity
2. Reduction of pain associated with peptic ulcer, which has been attributed to
An increase in gastric pH and subsequent buffering
An inhibition of the proteolytic action of pepsin by either adsorption by the antacid or
an increase in gastric pH
A protective coating action on the ulcerative tissue
Criteria for Non-systemic Antacids
While no antacid is ideal, there have been certain criteria that have been
developed. These are:
1. The antacid should not be absorbable or cause systemic alkalosis.
2. The antacid should not be a laxative or cause constipation.
3. The antacid should exert its effect rapidly and over a longer period of time.
4. The antacid should buffer in the pH 4-6 range.
5. The antacid should probably inhibit pepsin.
6. It should not cause irritation of the stomach and intestine.
7. It should not prevent absorption of foods, minerals, and vitamins.
Loss of antacid properties on aging
This is more of a problem with the dried gel than with the liquid suspension and is related to the
manufacturing process. Test results confirmed the loss of activity of aluminium hydroxide gel
preparations on drying and their variation in neutralising capacity. Physical data indicates that a
, change in gel structure occurs during the aging process. There are aluminum hydroxide gel
products on the market using polyhydroxy aluminium mono-carbonate hexitol complex
(Andursil®), which are claimed to stabilize the gel.
Combination antacid preparations
Because no single antacid meets all the criteria for an ideal antacid, several products are on the
market containing mixtures. Antacids are commonly used in combination for three reasons:
1. To combine fast and slow-reacting antacids in order to obtain a product with a rapid
onset and relatively sustained action. E.g., Mg(OH)2 (having a fast onset of action and
short duration of action) and Al(OH)3 (having a slow onset of action and prolonged
duration of action) are used together.
2. One component antagonizes the side effect of another component, e.g. mixture of
magnesium hydroxide (having laxative effect) and aluminum hydroxide/calcium
carbonate (having constipative effect) is done to balance the laxative effect and
constipative effect.
3. To lower the dose of each component and minimize the possibility of certain adverse
effects.
Combination antacid preparations
Aluminum hydroxide gel-magnesium hydroxide combination: does not cause
constipation or laxative. Dosage forms: suspension and tablet.
Aluminum hydroxide gel-magnesium trisilicate combination: In addition to the balance,
the magnesium trisilicate is supposed to exert its protective effect.
Magaldrate (AlMg2(OH)7·H2O): Magaldrate is a hydroxy magnesium aluminate complex
that is converted rapidly in gastric acid to Mg(OH)2 and Al(OH)3. It neutralizes gastric
acid very quickly.
1. Gastrointestinal hyperacidity
2. Reduction of pain associated with peptic ulcer, which has been attributed to
An increase in gastric pH and subsequent buffering
An inhibition of the proteolytic action of pepsin by either adsorption by the antacid or
an increase in gastric pH
A protective coating action on the ulcerative tissue
Criteria for Non-systemic Antacids
While no antacid is ideal, there have been certain criteria that have been
developed. These are:
1. The antacid should not be absorbable or cause systemic alkalosis.
2. The antacid should not be a laxative or cause constipation.
3. The antacid should exert its effect rapidly and over a longer period of time.
4. The antacid should buffer in the pH 4-6 range.
5. The antacid should probably inhibit pepsin.
6. It should not cause irritation of the stomach and intestine.
7. It should not prevent absorption of foods, minerals, and vitamins.
Loss of antacid properties on aging
This is more of a problem with the dried gel than with the liquid suspension and is related to the
manufacturing process. Test results confirmed the loss of activity of aluminium hydroxide gel
preparations on drying and their variation in neutralising capacity. Physical data indicates that a
, change in gel structure occurs during the aging process. There are aluminum hydroxide gel
products on the market using polyhydroxy aluminium mono-carbonate hexitol complex
(Andursil®), which are claimed to stabilize the gel.
Combination antacid preparations
Because no single antacid meets all the criteria for an ideal antacid, several products are on the
market containing mixtures. Antacids are commonly used in combination for three reasons:
1. To combine fast and slow-reacting antacids in order to obtain a product with a rapid
onset and relatively sustained action. E.g., Mg(OH)2 (having a fast onset of action and
short duration of action) and Al(OH)3 (having a slow onset of action and prolonged
duration of action) are used together.
2. One component antagonizes the side effect of another component, e.g. mixture of
magnesium hydroxide (having laxative effect) and aluminum hydroxide/calcium
carbonate (having constipative effect) is done to balance the laxative effect and
constipative effect.
3. To lower the dose of each component and minimize the possibility of certain adverse
effects.
Combination antacid preparations
Aluminum hydroxide gel-magnesium hydroxide combination: does not cause
constipation or laxative. Dosage forms: suspension and tablet.
Aluminum hydroxide gel-magnesium trisilicate combination: In addition to the balance,
the magnesium trisilicate is supposed to exert its protective effect.
Magaldrate (AlMg2(OH)7·H2O): Magaldrate is a hydroxy magnesium aluminate complex
that is converted rapidly in gastric acid to Mg(OH)2 and Al(OH)3. It neutralizes gastric
acid very quickly.
