Gastrointestinal agents are drugs used to treat gastrointestinal disorders like achlorhydria, hyperacidity, constipation, and diarrhea. Acidifiers increase acid concentration in the GI tract and are used to treat achlorhydria. Dilute hydrochloric acid maintains or increases stomach acid levels and pH. Antacids neutralize excess stomach acid in hyperacidity. Common acidifiers and antacids include ammonium chloride, dilute hydrochloric acid, and sodium bicarbonate.

1. Gastrointestinal Agent
Prepared by
Mr. Avinash B Thalkari
M.
Pharm
Subject: PIC

2. Gastrointestinal agents: These are the drugs which
are used in treatment of gastrointestinal disorders such
as achlorhydria, hyperacidity, constipation and
diarrhea.

4. Acidifying agent or Acidifiers: Acidifiers are the agent which
increases acid concentration in GI Track. These drugs are
used in treatment of achlorhydia.
The empty stomach has pH 1.5 -2 and rises to pH 5-6 when
food is ingested. The stomach has low pH because of the
secretion of HCl. Gastric HCl act by destroying the bacteria in
the ingested food and drinks. It softens the fibrous food and
promotes the formation of the proteolytic enzyme pepsin. This
enzyme is formed from pepsinogen at acidic pH (>6). Pepsin
helps in the metabolism of proteins in the ingested food.
Therefore lack of HCl in the stomach can cause Achlorhydria.
Therefore acidifiers like dilute Hydrochloric acid is used to
maintains or increases the level of hydrochloric acid in
stomach, thus maintaining proper pH of the stomach.

5. Acholorhydria: It is an condition in which there is
absence or insufficient secretion of hydrochloric acid
in stomach called as achlorhydria.
So dilute Hydrochloric acid is used to treat Achlohydria.
Dilute Hydrochloric acid helps to maintains or
increases the level of hydrochloric acid in stomach,
thus maintaining proper pH of the stomach.
Symptoms of achlorhydria:
•Abdominal & epigastric pain
•Loss appetite
•Mild diarrhoea
•Confusion
•Sensitivity to spicy food.
•Frequent movements of bowel.

6. Classification of Acidifying agent or
Acidifiers
Acidifying agent or Acidifiers are classified
in to four types
•Gastric Acidifiers
•Urinary Acidifiers
•Systemic Acidifiers
•Acids

7. •Gastric Acidifiers: These are the drug which are used to
increase the acidity of the stomach in patient suffering
from Achlorhydria. So dilute Hydrochloric acid is used to
treat Achlohydria.
Dilute Hydrochloric acid helps to maintains or increases the
level of hydrochloric acid in stomach, thus maintaining
proper pH of the stomach.
•Urinary Acidifiers: These are the drugs which are used to
remove acidic urine from the body or to maintain the Ph of
the urine.
•Systemic Acidifiers: These are the drug which is able to
neutralize the alkaline body fluids, especially blood.
•Acids: These are used as pharmaceutical aids in the
preparation of medicaments.

8. 1.Ammonium chloride*
Method of Preparation: 1. It is prepared by neutralization of
hydrochloric acid using ammonium hydroxide and evaporate the
solution to the dryness followed by crystallization.
NH4OH +HCl NH4Cl + H2O
It is prepared treating ammonia with HCL.
NH3 + HCl NH4Cl
Assay:
Principle: Assay of ammonium chloride is performed using back
titration.
Procedure:
Take a conical flask and add 0.1 gm ammonium chloride & 20 ml
distilled water then add 1.5 ml of conc. Nitric acid, 2.5 ml nitrobenzene
& 25 ml sliver nitrate (0.1N). Titrate above solution with Standardized
solution of ammonium thiocynate using 2 to 3 drops of ferric
ammonium sulphate as indicator. End point is colourless to redissh
brown.

9. Properties :-
Physical properties:
•It occurs as white colorless, crystalline or a coarse powder.
•It is odorless.
•It has cooling saline taste.
•It is slightly hygroscopic in nature.
•It is very soluble in water, sparingly soluble in alcohol and freely
soluble in glycerin.
•Freshly prepared aqueous solutions are neutral to litmus but become
quickly acidic on standing due to hydrolysis.
Chemical properties: On heating it loses a acid
NH4Cl HCl + NH3
On reacting with strong sodium hydroxide base it liberates ammonia
gas.
NH4Cl + NaOH H2O + NaCl + NH3

10. Uses:
•It maintains acid-base equilibrium of body fluids.
•It exhibits diuretic effect.
•It is used as systemic acidifiers.
•It is used in lead poisoning.
•It is used in treatment of UTI.
•It acts as thickening agent in hair shampoos preparation.
•It is also act as a flavouring agent.
•It acts as mild expectorant. Therefore it is used in cough
preparation because of local irritation this produces
increased secretion of respiratory tract and makes the
mucus less viscous.
•It is used as emetics.

11. Dilute Hydrochloric acid
Properties:
Physical properties:
It is clear, colorless fuming liquid.
It is tasteless.
It is punjent in odour.
It is soluble in water & alcohol
It is acidic to litmus.
It has specific gravity of about
1.18.
Uses
•It is used as acidifying agent.
•It is used as pharmaceutical aid.
•It is used as reagent in various strength.
•Used in treatment of achlorhydria.
•Act as solvent.

12. ANTACID: Antacids are the agent or substances which neutralize the
excess of hydrochloric acid in stomach are called as antacid.So it is used
in hyperacidity .
Ideal properties / Requirement / Characteristics of antacids:
Insoluble in water except systemic antacid e.g. sodium bicarbonate
Should have fine particle size
should not be absorbable
should not causes constipation
should not be act as a laxative
should exert effect rapidly
should not causes systemic alkalosis
Should effect over a long period of time
Should not causes evolution of large amount of gas(by reacting with acid in git)
Probably inhibit pepsin
Easily available
Non toxic
not causes any side effect
should be stable
Antacid should be inexpensive and palatable.

14. Combination of antacid preparations
As single antacid cannot meet all the requirements for an ideal antacid,
it is very difficult to prepare single ingredient antacid preparation
without side effects. Hence most of antacid preparations are available
in market in the form of combination. Most of the combinations are
based on two principles-
In an attempt to balance the constipating effect of calcium and
aluminium compounds, they are combined with laxative effect of
magnesium compound.
•Some of these products contain a fast acting antacid with others
having longer duration of action.
•The antiflatulent or defoaming agents such as dimethicone,
simethicone and reflux suppressants such as alginic acid may be
added for quick action.
Few examples are – i)Aluminium hydroxide gel – Magnesium hydroxide
•Aluminium hydroxide gel – Magnesium trisilicate
•Calcium carbonate containing combination Alginic acid containing antacid
combination.

15. Sodium bicarbonate
Methods of preparation: The brine solution(NaCl) is saturated with
ammonia to removes impurities, the solution is filtered and passed
through the carbonating tower .In this it is allowed to react with a
current of CO2 and the tower is cooled to enhance precipitation . The
precipitation is filtered out and dried.
In the laboratory it is prepared by passing CO2 gas
through solution of sodium hydroxide. The solution is
concentrated to obtain the product

16. Assay:
Principle: It is based on acidimetric method.
Procedure:
Conical flask: Weigh accurately 1.5 gm of sodium
bicarbonate and dissolve in 50 ml water.
Indicators: Then add 0.2 ml of methyl orange
solution as indicator.
Burette: Titrate the solution with standardized
hydrochloric acid,
End point: until the solution become pink.

17. Physical properties:
•It is white coloured crystalline powder.
•It is odourless
•It is saline in taste.
•It is soluble in water.
•It is insoluble in alcohol.
•It is alkaline in nature in aqueous solution.
•It is having ph 8.2 in aqueous solution
Chemical properties: It is stable in air but decompose in
presence of heat or moist air.
2NaHCO3 H2O + CO2 + Na2CO3
•When it is treated with sulfuric acid the sodium sulphate (salt) &
water formed.
2NaHCO3 + H2SO4 Na2SO4 + 2H2O + 2CO2

18. Uses:- Sodium bicarbonate
•It is used as systemic antacid.
•It used as electrolyte replenisher.
It is used in the treatment of acidosis.
•It is used as expectorant.
•To produce systemic alkalosis.
•It is used in formulation of eye drops and ear drops to
remove the wax.
•It is used to control the vomiting.
Its 1-2% solution is used for rinsing the contact lens.