The document discusses various inorganic agents used to treat gastrointestinal diseases, categorizing them into four types based on their mechanism of action, including products for altering gastric pH, intestinal inflammation, adsorbents for toxins, and laxatives. It explains conditions like achlorhydria and hyperacidity, along with treatments involving acidifying agents and antacids, highlighting the differences between systemic and non-systemic antacids, their ideal criteria, and side effects. It also covers specific examples of antacids and their preparations, emphasizing the importance of combining antacids to achieve optimal therapeutic effects.

1. GASTROINTESTINAL
PRODUCTS

2. INTRODUCTION
• THE INORGANIC AGENTS USED TO TREAT GASTROINTESTINAL DISEASES ARE
DISCUSSED HERE. ON THE BASIS OF MECHANISM OF ACTION INORGANIC
GASTROINTESTINALAGENTS ARE OF FOLLOWING FOUR TYPES-
1. PRODUCTS FOR ALTERING GASTRIC PH
a) ACIDIFYING AGENTS (INDUCE ACID SECRETION) E.G. HISTAMINE PHOSPHATE
ETC.
b) GASTRIC ANTACIDS E.G. AL(OH)3, NAHCO3 ETC.
2. PRODUCTS FOR INTESTINAL INFLAMMATION (PROTECTIVES) E.G. BISMUTH
SUBCARBONATE.
3. ADSORBENTS FOR INTESTINAL TOXINS E.G. ACTIVATED CHARCOAL.
4. CATHARTIC OR LAXATIVES FOR CONSTIPATION E.G. MGSO4, MG-CITRATE ETC.

3. Products for altering gastric pH
Functions of gastric HCl
1. Gastric HCl functions by killing the bacteria in ingested food and drink.
2. It softens fibrous foods.
3. It activates the inactive proteolytic enzyme pepsinogen into pepsin.
4. It causes hydrolysis of all the food stuff.
5. It keeps iron in ferrous state for absorption.
6. It converts collagen protein into gelatin.
7. It helps in maintaining a proper environment for gastric emptying.

4. Dysfunctional HCl secretion
Achlorhydria
Achlorhydria is the disorder due to reduced secretion of HCl in the gastric
secretions. Patients with this condition fall into one of the two groups-
A) Patients who remain free of gastric HCl secretion after stimulation with histamine
phosphate.
Causes:
i. Subtotal gastrectomy (partial removal of stomach)
ii. Atrophic gastritis (chronic gastritis with atrophy of the mucous membranes and
glands)
iii.Carcinoma of the stomach etc.

5. A) Patients in whom there is normally a lack of gastric HCl but who respond to
stimulation by histamine.
Causes:
i. Chronic nephritis (inflammation of the kidney)
ii. Chronic alcoholism
iii.Tuberculosis
iv.Hyperthyroidism
v. Pellagra, sprue (a periodic fatty, frothy diarrhea) and parasitic infestations.
After age of 50 it (B) is common in individuals.

6. Gastric hyper secretion
When an excess amount of gastric HCl is secreted the condition is called hyperacidity. When
hyperacidity develops, the result can range from gastritis (a general inflammation of the gastric
mucosa) to peptic ulcer (specific circumscribed erosion).
Peptic ulcer:
Peptic ulcer is the break in the continuity of the mucosa of any part of GIT caused by HCl
and pepsin.
Treatment of achlorhydria–acidifying agent:
i. Diluted HCl N.F. has been utilized to relieve first type of achlorhydria.
ii. Administration of histamine phosphate is the treatment recommended in second type of
achlorhydria.

7. Antacids
Antacids are basic compounds which neutralize excess gastric HCl
(associated with gastritis and peptic ulcers).
They neutralize by reacting with HCl to form salt and water.
Antacids are classified into
1. Systemic antacids
2. Non-systemic antacids

8. Systemic drugs
A drug which is absorbed from stomach or intestine and flows in the systemic
circulation is called systemic drug.
Simply a drug which is distributed through systemic circulation is a systemic
drug.
The antacids which are soluble in the gastric fluid and readily absorbed from
the intestine into the circulation, capable of causing systemic electrolyte
disturbances and may produce symptoms of alkalosis are called systemic antacids

9. Non-systemic antacids
The antacids which are insoluble in gastric fluid and insignificantly absorbed from the intestine
due to formation of insoluble compounds so that they don’t cause any systemic electrolyte disturbances
are called non-systemic antacids.
Comparison between systemic and non-systemic antacids:
Feature Systemic antacid Non-systemic antacid
solubility Soluble in gastric fluid Comparatively insoluble in gastric
fluid
Absorption Readily absorbed from intestine Absorption from intestine is near zero
(insignificant)
Mechanism of action They are absorbed into the circulation
from where they reach the site of
action
Directly act on the site of action
Electrolyte disturbance Capable of producing systemic
electrolyte disturbances
Do not produce systemic electrolyte
disturbances
Effect on pH May produce systemic alkalosis They don’t produce such systemic
effect
Example NaHCO3 Al(OH)3, Mg(OH)2

10. Ideal criteria of antacids
1. It shouldn’t be absorbable or cause systemic alkalosis
2. It shouldn’t be a laxative or cause constipation
3. It should exert its effect rapidly and over a long period of time i.e. it should have a short on-set of
action and long duration of action.
4. The antacid should buffer in the pH 4-6 range (the antacid should neutralize HCl to give a pH of
4-6).
5. It shouldn’t cause a large evolution of gas by reacting with gastric acid
6. It should probably inhibit pepsin
7. It shouldn’t cause irritation to stomach & intestine
8. It shouldn’t prevent absorption of food, minerals and vitamins.
9. It should be palatable, cheap and available.
[On-set of action: The time required for the drug to be active
Duration of action: The time period for which the drug is active]

11. Specific examples of antacids
i) Al(OH)3
It is an example of non-systemic antacid. In therapy Al(OH)3 occurs in two
physical forms.
a) Al(OH)3 gel → A white viscous suspension
b) Dried Al(OH)3 gel → It is a white, odorless, tasteless, amorphous powder
insoluble in water and alcohols but soluble in dilute mineral acids solutions of
fixed alkali hydroxides.

12. Commercial manufacture:
)
(
3
3
2
3
3
2
alum
potash
2
4
2
4
2
3
2
3
2
2
4 CO
SO
K
SO
Na
Al(OH)
O
H
CO
Na
)
KAl(SO 






Distilled water is heated and divided into 2 parts. In one part potash alum is added and in the other
one Na2CO3 is added. Thus a solution of potash alum and Na2CO3 is prepared. The solutions are
mixed together and the ppt of Al(OH)3 is washed with water. Each time after washing BaCl2 is added
and filtered for confirmation of absence of SO4
2-.
After properly drying, the weight of the obtained Al(OH)3 was measured and the yield value was
calculated.
100


amount
Target
amount
Obtained
value
Yield

13. Side effects of Al(OH)3 gel:
i. It can cause constipation.
The product of reaction of neutralization is AlCl3 is a water soluble astringent. (Astringents
are those agents which can cause constriction of tracts/vessels)
ii. Continued use of these antacid causes phosphate deficiency. In this case insoluble
aluminum phosphate salt is formed which is excreted from the body.
iii. Can cause nausea and vomiting.
iv. It may interfere/reduce the absorption of other drugs like tetracycline. Al(OH)3 forms
complex with tetracycline. Thus they can’t be administered simultaneously.

14. i) Mg(OH)2
Mg(OH)2 is a white, odorless, fine amorphous powder. It is practically insoluble in water and alcohol but
soluble in dilute acids. The milk of magnesia is a suspension of Mg(OH)2 and may contain 0.1% citric acid
and & more than 0.05% volatile oil or a blend of volatile oils.
Preparation:
It is prepared by boiling MgO in water and drying the base so obtained
Citric acid may be added to minimize the interaction with the glass containers.
Safety:
i. In high dose, Mg(OH)2 is works as a laxative.

15. Simethicone:
Simethicone is not an antacid but it is used as an active ingredient in antacid
preparations. It is an antiflatulence (flatulence is the presence of excessive gas in the
stomach and intestine) agent frequently used in antacid preparations to defoam gastric
juice in order to decrease the incidents of gastro-esophageal reflex.
Acid neutralizing capacity (ANC):
Acid neutralizing capacity is the measure by which antacids are quantitatively
compared. It is defined as the quantity of 1N HCl (expressed in mEq) that can be
brought to a pH 3.5 in 15 minutes by the unit dose of antacid preparation.

16. Combination antacid preparations:
Antacids are used as combinations for three main reasons-
i. To get rapid on-set (short on-set of action) and to get sustained action (prolonged
duration of action). Mg(OH)2 has a fast on-set and short duration of action whereas
Al(OH)3 has slow on-set and prolonged duration of action. Thus in the mixture these
effects are maximized.
ii. To antagonize side effects of each other. For example Mg(OH)2 has laxative effect and
Al(OH)3 has constipating effect. Thus in the mixture these effects are balanced. To
lower the dose of each component

17. Side effects of antacid therapy:
Acid rebound:
Most antacids used today raise the gastric pH to 4-5. This pH reduces proteolytic action of
pepsin. In an attempt to maintain a lower gastric pH, the stomach secretes additional HCl. The
result is that excess of HCl is secreted into the stomach. Thus possible hyperacidic condition may
rise. This condition is called acid rebound which could further aggravate into ulcer.
Systemic alkalosis:
Systemic antacids may exert alkaline effects on the body’s buffer systems.
Local effects in the GIT:
Antacids containing calcium and aluminum salts tend to be constipating due to formation of
water soluble salts from neutralization. On the other hand antacids of magnesium salts tend to be
laxative.

18. What are the problems of CaCO3 as antacid?
The reasons are given below-
i. Ca2+ is partially absorbed from the GIT and cause milk-alkali syndrome
ii. Ca2+ is deposited in the kidney
iii.CaCO3 diffuses in stomach and directly (by parietal cells) and indirectly
(by stimulating gastrin) causes HCl secretion.